Kitesail Apprentice

Function: A creature for White Weenie. As I have proposed in the past, I would believe that the path for White Weenie to take would be the evasive route because of the inevitable "creature creep" where creatures get made better and better while White Weenie cards don't evolve past WW 2/2s with abilities. This flies and gets a size bonus when equipped, making him a very suitable inclusion into the White Weenie deck that I am advocating.
Requirements: Cheap equipment such as Bonesplitter, Shuko.
Decks: White Weenie.

Kor Firewalker

Function: Sideboard against red. This card is half Warmth and half Silver Knight. Both halves make life slightly better against red but is still vulnerable to cards like Pyrite Spellbomb, Ghostfire or Culling Scales. The WW cost is the most prohibitive part about this card which would otherwise shine more than what I expect it to at this point in time.
Requirements: Consistent access to WW mana.
Decks: White Weenie, Rock decks, UW control.

Loam Lion

Function: Aggressive beater, Kird Ape#2. As of the late, we've been getting W for 2 power at a consistent rate. Of course, functionality-wise, this does not compare directly to say Savannah Lions because they belong in different decks altogether. Loam Lion needs a home in a deck that has a healthy access to lands unlike its White Weenie counterparts who can live on minimally small patches of plains. Its buff size makes it desirable to play in a 2-3 colored aggressive deck.
Requirements: Fetchlands and dual lands for highest efficiency.
Decks: Zoo, Naya, GW beats.

Refraction Trap

Function: Sideboard against decks with burn spells. A larger Harm's Way effect that can be potentially the same cost. Burning your own threats is as bad as it gets for a deck that needs card volume to win. That said, it is possible that you might end up having to cast it at 4 mana in many games when your opponent just beats you with creatures so you need to plan your moves in advance based on the general outlook of the opponent's deck.
Requirements: A play style that can lure out burn spells at crucial points in a game, cautious with when or not to leave mana open to cast it.
Decks: Decks that plays with creatures and with access to white mana.

Stoneforge Mystic

Function: Fetch out powerful equipments such as Sword of Fire and Ice, Sword of Light and Shadow or even a Shuko to target a Cephalid Illusionist. The second ability lets the equipment move into play past counter magic and that can have a very significant impact on the game. Her cheap cost makes her exceptionally powerful like many other 2cc bombs like Tarmogoyf or Bitterblossom. A very high power card, like white's very own unique... Goblin Lackey? She also opens up to an equipment toolbox to let her get the right threats against the right matchups.
Requirements: Advisable to run at least 2 equipments.
Decks: White Weenie, GW beats, Rock, Zoo, Naya. Supports mainly creature based decks, easily splashed.

Jace, Mind Sculptor

Function: Gives card advantage. Unlike Jace Beleren, it would be difficult to enjoy the mileage of card drawing because a starting loyalty of 3 makes him very vulnerable. The most intuitive play, as with most planeswalkers, would be to up the loyalty counters to 5 before using his Brainstorm ability but that doesn't really impact the game at that point in time. Being a 4 mana sorcery speed card makes this version of Jace very different from the previous version which could give more control over the game state by not having to change the intention of drawing cards. Jace Beleren could come down on turn 3 or turn 5 with protection. You can opt to give your opponent a card or not but you ultimately got your card. At the very least, you would have cycled Jace Beleren away. If you gave your opponent a card, odds are high that he would try using it to knock off Jace's loyalty counters, using up mana and the drawn card from before and that would change the flow of the crucial turn.
The new Jace is very bad naked. You play him at the expense of many other 4cc cards and at a point in time when you should start molding the board position. He is hard to hold protection for. Still, Brainstorm + fetchlands is almost a draw 3 effect but 4 mana for a Brainstorm is not too appealing so you need to have more interactive elements in your deck to ensure that Jace, Mind Sculptor can do his thing.
Requirements: A blue deck that can afford being tapped out on turn 4.
Decks: A deck that runs mainly on blue mana. UB control (depending on how aggressively built it is), UW control (if there are more creatures to block with), UG aggro-control, Crosis (possibly as it taps out often).

Sejiri Merfolk

Function: Powerful merfolk to beatdown with (if you have a plains out).
Requirements: At least a deck which has greater (or equal) access to blue than white and has easy access to plains via fetches + duals.
Decks: UW fish.

Spell Contortion

Function: Counter magic with access to card draw. This card, like Jace, Mind Sculptor, works better in a slower environment. 3 mana for a Rune Snag is very weak but it gets better with everytime it gets kicked. 5 mana for pay 4 or counter + draw a card. 7 mana for pay 6 or counter + draw 2 cards. It works well in an environment that runs more clunky spells (because cheaply costed decks can play around paying mana) and few counters (because you can't counter the opposing counter when you are tapping out).
Requirements: A play style that leaves mana open very often.
Decks: UB control, UW control.

Thada Adel, Acquisitor

Function: Control hate, sideboard material. You will always have a target to get against blue based decks, be it a standalone Sensei's Divining Top, a Seat of the synod or even threats (if you have the mana to play them). Unblockability is a very strong asset in the control matchup because of how integral blocking is to a control decks ability to stabilize. Unfortunately, having a 3 mana 2/2 against any other deck is probably going to make people laugh at it so I would suggest putting him into the sideboard to prey on island playing folks.
Requirements: Opponent playing with islands.
Decks: Decks that run with heavy blue mana.

Treasure Hunt

Function: Card draw. Fortunately, most decks run a healthy ratio of lands in the format so you can enjoy the minimum of 1 to the unlikely limit of 30+ card draw that is said to average at 1.75 cards in the standard format. (I do believe that that number is a nice gauge in 100 card Singleton as well) Playing this card well requires strong intuitive skills as to how to manage the cards because it plays at sorcery speed. Also, the big factor to consider is that there will only be one business spell that comes along with it and it would be revealed.
In different games, the weightage of the usefulness of mana is different. Against a control matchup, having the mana advantage is a key factor in beating the war. Against aggressive decks, having sufficient mana is the most important factor to survive. Therefore, the timing of Treasure Hunt needs to vary for these decks because it's a 2 mana card that can be easily misplayed to lose incremental advantages. As a word of advice, run it early against fast decks and play it leisurely against slow decks at openings that you can find. You need to be greedy when the time comes and you also need to have the discipline to move away from greed.
Cards like Scroll Rack and Brainstorm work very well with this as you can set up a larger land pocket to draw into. Psychatog can benefit from a sudden jump in the hand size from a Scroll Rack + Treasure Hunt.
Decks: Any deck with a minor blue splash, best with a high ratio of lands.

Wind Zendikon

Function: Make a 2/2 flier or reuse a land that dies naturally. Over its main function, I'm slightly more interested in its secondary function of being able to reuse cards like fetchlands or Wasteland. Summoning sickness, or whatever it is called today, is going to be the downfall of some people who don't take note of it in regards to this aspect when they find out that their Wasteland is down for the turn.
As a 2/2 flier, there are cards such as Flagstones of Trokair, (God's Eye, Gate to the Reikai) or even the indestructible Darksteel Citadel that can increase the value for this enchantment. 
Requirements: Blue mana.

Abyssal Persecutor

Function: 4 mana 6/6 flying trample monster. The stats are as good as it gets, trumping even the classic Juzam Djinn. The stats suggest that you want to be aggressive. Unfortunately, it is on the card itself that says your opponent can't lose as long as it is in play so there is a need to dedicate answers that can hit it or have means to let it go away. Proper planning with regards to the board state is very important because you might end up killing yourself. If you deal lethal damage and you can't get rid of it, you still lose when lethal damage comes unto your head.
Requirements: Efficient ways to remove it without damaging the deck's function. 
Decks: Aggressive decks that have access to BB on turn 4 and control decks that want to add fast pressure.

Anowon, the Ruin Sage

Function: 4/3 for 5 mana that eats up a non-vampire on your upkeep. I would think that this is a good sideboard card against decks that run beefy creatures. He's decent in the maindeck too but there are not too many scenarios whereby you would want a 4/3 at 5 mana over a 5/5.
Decks: Sideboard of midranged decks to fight other midranged decks.

Nemesis Trap

Function: Sideboard against decks that run white creatures such as zoo or the obvious White Weenies. In the best case scenario, you get to kill 2 creatures for just BB. The second to that is that you get to kill just 1. You would hardly ever play it for its full retail cost unless something went really wrong.
Decks: Decks that give you access to BB at a consistent rate.

Urge to Feed

Function: BB for -3/-3 at instant speed. The tap a vampire to put a +1/+1 counter on it is a bonus that not many people would ever get to enjoy. Changelings maybe?
Decks: Decks that give you access to BB and have an occasional vampire to pump so that there is a reason to play this over Last gasp. Suicide black?

Chain Reaction

Function: Board sweeper that varies in intensity. You would probably use this as a Pyroclasm or Firespout of some sort. It fits against decks that run a bunch of creatures that you might have trouble with such as decks with creatures that have varying toughnesses that go beyond 3. A very metagame dependant card that is good to have lying around in your collection.
Requirements: A board situation with enough creatures to kill what you want to kill and you need to beware of instant removals to change the numbers around.
Decks: Zoo, Naya against swarms/mirrors.

Comet Storm

Function: A Volcanic Geyser that can make copies of itself. It becomes better the longer you are able to drag the game, being able to take down multiple bombs as long as you have the mana required. The main card to compare this with is Starstorm which can also fulfil a board controlling function but cannot hit players. You want to play this when you yourself are playing strong creatures such as Baneslayer Angel to get rid of opposing ones. Being able to shoot Planeswalkers via players also gives you a reason to play this over Starstorm.
Requirements: A ton of mana.
Decks: URW Control/ UR control.

Dragonmaster Outcast

Function: A 1/1 that can be fetched out via Ranger of Eos. This is one of the main reasons why this card might see play. I highly doubt that a mono red deck would want a mere 1/1 that can only impact the game late. Proclamation of Rebirth works with this card too.
Requirements: A deck that might have 6 lands in play.
Decks: Naya.

Quest for the Goblin Lord

Function: Let your team of goblins get a +2/+0 bonus by playing goblins. It's almost a win more card but not entirely so. It does turn your mediocre board of a bunch of goblins into a painful bunch of goblins. Works best if you have a high ratio of goblins with minimal burn spells. It's not the best card to play but the variance of the format might actually make this playable.
Decks: Goblins.

Ricochet Trap

Function: Antiblue sideboard. Yet another way to make the blue mage sad. This time, you can steal Thirst for knowledge and still counter counters. However, in doing so, you lose a subset of cards such as creatures (which you can Pyroblast) or untargeted draws such as Fact or Fiction or double targeted Cryptic Commands.
Decks: Any deck with red that wants to redirect a blue spell.

Searing Blaze

Function: Creature kill. If you play Lash Out, you might want to consider playing this over that. There are some minute differences such as the need for landfall and not being able to fix your draw but damage-wise, this is a Lash Out + clash win that has 2 targets. You might want to shy away from Searing Blaze if your deck is low on lands unless you are willing to hold up at least one land if you are waiting to draw it.
Decks: Decks that play RR spells.

Slavering Nulls

Function: A goblin specter. A nice addition to the RB goblins as it's at least a 2/1 that gains a specter bonus if you have a swamp in play.
Requirements: Swamps, ideally with tons of fetches and dual lands.
Decks: RB goblins or any RB aggressive deck.

Arbor Elf

Function: Mana elf. There are a few reasons why you might want to play this over Llanowar Elves.
#1 Non-green colored mana from dual lands.
#2 Untapping forests with enchantments on them.
The biggest question here as to whether or not to play this card is how consistent one can have access to a "forest" because most people like non-basic lands. If you have that well thought out, Arbor Elf might be worth gold.

Groundswell

Function: G for 4 damage. Yet another huge green pump spell for the unorthodox mono green aggro strategy. This looks promising because it is easier to cast without resistance unlike some others that need you to cast before blockers
Decks: Mono green aggro. 

Leatherback Baloth

Function: Cheaply costed fatty, hard to kill via damage although almost every black removal gets it. Still, it has the capability to pressurize opponents and get in for fast damage. If this comes down on turns 2/3, it would probably deal 8 damage on its own.
Decks: Any mono green deck.

Nature's Claim

Function: A Naturalize for G. The most special part about this card is its cost which is dirt cheap which you can run in a mana tight deck, assuming the life gain is not going to be of any importance.
There are some cards that react to your opponent gaining life such as False Cure, Kavu Predator and Punishing Fire so this might go into decks spotting those cards too.

Wolfbriar Elemental

Function: A wolf dumptruck. A basic body of 4 mana 4/4 that spits out 2/2s for every additional G. Very very strong against creature based decks.
Requirements: A mana base that is heavy green.
Decks: Rock, Mono green decks.

Novablast Wurm

Function: A 7/7 that sweeps the board. A good reanimation target as you would almost never lose to a creature race with this card in play when you actually might, in various situations, like even with an Akroma, angel of wrath in play.
Requirements: A deck that stalls long or a reanimation deck.
Decks: Rock (sb against mirror), Reanimator.

Wrexial, the Risen Deep

Function: Bomb. At 6 mana and double landwalk, this is almost unblockable against most slower decks. It's hard to kill and it's unblockable. A really powerful card that would take games. Its 5/8 body at 6 mana is way bigger than the industrial standards for aggressive creatures in the format. The only cards I see beating through this are cards with deathtouch or a full-sized Tarmogoyf which are said to be very rare. Reanimator can also play this card but its effectiveness is varied across matchups so I don't really recommend this in the maindeck of reanimator.
Decks: UB control, reanimator. 

Basilisk Collar

Function: Turn your creature into a Vampire Nighthawk without flying. The neatest thing about this card is that it is a "trinket" (1 mana artifact) which means Trinket Mage can fetch it out. Being an artifact also means that any deck can play it. If you stuck this to a creature that is hard to kill like Troll Ascetic or Phantom Centaur, you probably would win against any red decks. If you are playing a blue based deck and stuck this to a dragon, you would probably turn the tides over against any decks trying to race you.
I see this as a cheap Loxodon Warhammer.
 

Everflowing Chalice

Function: A mana artifact that can be searched via Trinket Mage, pop out free from Dark Confidant or (Ad nauseum) and can be upsized into (Eye of ur-golem) or bigger (which you would hardly need). The only drawback is that it provides only colorless mana. Very useful for a deck that runs on a good amount of colorless mana.
Decks: UW control.
 

Lodestone Golem

Function: Mana disruption in a relatively large sized body. With mana producers such as (City of Traitors) and Ancient Tomb in the format, this card is more than playable. Artifacts are not that rare but most people don't play that many of them so it tends to be a one sided (Sphere of resistance) in most cases.
Unfortunately, toughness 3 is not hard to overcome but you might be able to get enough tempo with its presence for it to not matter.
Juggernaut looks so weak now.

 

Pilgrim's Eye

Function: A colorless Civic wayfinder. Helps you fix your mana but is ideally for decks that can abuse "enter the battlefield" effects because there are better alternatives to obtain basic lands that cost cheaper and can help you get out of a mana screw situation.

Bojuka Bog

Function: Maindeckable graveyard hate with minimal disruption to the progress of the board. Also possibly a Living Wish target. Obviously, best in a deck that uses black mana but it has no restrictions and can be a pseudo colorless land.

Celestial Colonnade

Function: A Serra Angel in a land but doesn't serve its dual function of both attacking and blocking unless you have a large amount of mana. Even so, having a 4/4 flier hiding in a land is plain goodstuff.

Creeping Tar Pits

Function: An embodiment of the style of UB, somewhat like a Vendilion Clique version of a manland. The 3 power is an ideal stat for both attacking and trading with Treetop village. It can easily threaten the game state as it is unblockable. Control decks don't have many good options when they can't use creatures to block this.

Dread Statuary

Function: A colorless beater that is easily traded with. It sinks up 4 mana so you are essentially using 5 lands to attack with a 4/2. Providing colorless mana in an aggressive deck probably means that this can only go into less color intensive aggressive decks. (I assume it wouldn't be used defensively because it makes you really vulnerable to tricks.) A mono red that does not run RRR spells comes to mind. 

Halimar Depths

Function: A land that lets you arrange the top 3 cards at the expense of entering the battlefield tapped. It's really good for a control deck on any turn but turn 2 since most blue based decks don't have that much to do on turn 1. Aggressive decks don't have a real reason to play a land that comes tapped. A mid-ranged deck would also be able to benefit from this land unless it's a deck that runs a good number of lands that come tapped already.
One would need to balance the number of lands that enter the battlefield tapped if one would want to play this card.

Khalni Garden

Function: Having a free 0/1 body has its uses. It helps convoke (from Ravnica's selesnya guild) or decks that try to Polymorph tokens/lands into fatties. Putting down equipment or Rancor on this for fast beats is also possible.
Similar to Dryad arbor but isn't a forest and can't be killed. I like this better.

Lavaclaw Reaches

Function: A very situational card that can pressure your opponent by just being around because it is always possible that you can clear away a lone blocker and sink in all your mana into tons of damage. Of course, compared to all the other manlands, this looks the weakest because it's the easiest to trade with but it's also very dangerous as described above and there is no need to keep turning it into a beater when it looks unfavorable to do so. Not a card to underestimate.

Raging Ravine

Function: You paid 3 mana to deal 3 damage with Treetop village. Here comes its big brother that, when attacking for the first time, is a 4/4 for 5 mana. The fact that it grows is a huge pain for control decks that like to keep mana open because it becomes more troublesome to deal with each swing. It already escapes sorcery speed kills like Treetop village did and is now fatter. Most creatures that control decks run don't deal with creatures with 4 toughness very well. This and (Bloodbraid Elves) makes RG a very alluring color combination to have in a deck. However, you will need to be able to sacrifice the consistency of a mana curve as you play more lands that come in tapped.

Sejiri Steppe

Function: A land that gives protection at sorcery speed. The main use of this card would be to punch through a creature through defenses. Best with large creatures but also good with small decks that are aggressive in nature.
Decks: White weenie, Rock.

Stirring Wildwood

Function: A 3/4 "spider" manland. Its true value comes from the fact that it belongs to a color combination that enjoys colored mana and can take advantage of an occasional creature popping out of the blue to mess up combat.
Its reach is rather useful because it actually stops a good number of fliers in the format such as Vendilion Clique or even (Meloku, the clouded Mirror). Not to mention that it can actually give you an extra turn against a Baneslayer Angel.
A very powerful defensive card.
 

Tectonic Edge

Function: A second Wasteland. Although it looks really similar to Wasteland, there are many fundamental differences. Firstly, it doesn't mana screw your opponent (unless mathematical variances are on your side) as he would have a bunch of lands out already. Secondly, you need 1 more mana to do its thing. Tectonic Edge is probably a card for slower control decks to get rid of annoying lands. I don't see aggressive decks needing this card.