Pestilence

It might have been printed, AT COMMON, in SEVEN different sets, but none of them have ever been online!  In the meantime, I've made more decks using Pyrohemia, Withering Wisps, and the Ashling avatar than I even care to admit, but none of that will stop me from buying a playset of these the second they're available.  My Erg Raiders demand it.

As far as vanguard goes, any avatar that offers a toughness boost should help your guys survive, from Arcbound Overseer to Raksha.

Skittering Skirge

I'll put it this way.  Illusory Demon has made the cut in my decks before.  And this guy is a lot better than Illusory Demon.  (Aside from being cheaper, read their text boxes carefully: this guy sacrifices to creatures only, not every spell.)  I already have several decks this guy would be right at home in, including a RB aggro Higure avatar deck, a monoblack Circling Vultures / Prodigal Sorcerer avatar deck, a couple of Haakon avatar decks, and a couple of spell-heavy control decks.  And I have one new deck in mind I plan to make:

This guy plus the Nekrataal avatar!  Casting a 3/2 flier on the first turn is borderline unfair (although still markedly less so than what that avatar is usually used for).  The strategy is slightly weakened by the Skirge's drawback conflicting with the avatar's gameplan, but does it really matter?  When you have a 3/2 flier on the first turn?

Waylay

The infamous Waylay trick might not work anymore, but there's still plenty of fun to be had with this card.  An avatar like Oni of Wild Places gives the tokens all haste, bringing them right back to the "White Lightning" glory days they once had.  And (I think this works) casting Waylay in front of a Fallen Angel avatar causes a Lightning Helix-sized swing in life totals.  In addition to taking out a few attackers.

Flesh Reaver

Before this card came out, the conventional wisdom was that if black got a low-cc creature that made you lose life, it was good, period, no questions asked.  (Remember, this was the heyday of suicide black, with Carnophage, Hatred, and Dark Ritual all standard legal.)  Flesh Reaver was really the first creature to make people rethink that formula.  Because it made you lose a LOT of life, even when it was just getting chumped by a Llanowar Elves.  Which it would.  This was also the heyday of elf decks, with Priest of Titania and Gaea's Cradle running rampant.

Still, in the realm of vanguard, I'm unafraid of Flesh Reaver's drawback.  Avatars like Serra Angel or even Loxodon Hierarch can skyrocket your life safely above your opponent's, making this guy a lot safer an investment.  He could also be good with the Platinum Angel avatar, to keep you alive through his damage.  And speaking of damage, notice that he deals you damage, not makes you lose life, meaning he could combo pretty well with the Stuffy Doll avatar.

Spined Fluke

I already made an Erhnam avatar deck that used the EtB saproling tokens to feed cards with EtB sacrifice triggers, like Kjeldoran Dead and Commander Greven il-Vec.  I wanted to use Spined Fluke in there at the time, and I'll still want to do it once this card is in print.

(Tellingly, I never did want to use Accursed Centaur in there.)

Victimize

It's technically an overstatement, but not much of one, to say that this is playable in any deck with creatures and black mana.

And still, its playability only increases in vanguard.  Think of all the Teysa avatar decks you've seen that end up with packed graveyards and a few 1/1 spirits in play.  Would they have any trouble casting this spell?

Then there are all of the aggro-friendly avatars, from Vampire Nocturnus to Goblin Warchief, who would love to play this card.  And this is before we even get the Momir avatar, which simultaneously gives Victimize targets and fodder.

Acidic Soil

To be fully honest, I hadn't even heard of this card until I was running through the Gatherer search for this article.  But immediately my mind jumped to the Stuffy Doll avatar, which would be positively brutal next to this card.  (Supposing each player has 6 lands in play, it's dealing 9 to your opponent and only 3 to you.)

It also could be good in a burn deck, which vanguard creates many opportunities for, because it gives you a mid- / late-game plan that can deal serious damage for a very low cost.  (Fun fact: the first ever sligh deck used Dragon Whelp as its mid- / late-game plan.)

Somewhere out there is probably a Johnny planning ways to combo this with Sky Swallower.

Thran Turbine

Seems like quite a drawback, doesn't it?  Back in the day, there wasn't so much to use this on besides an occasional Jayemdae Tome.  But as all vanguard players know, there is so much more to spend mana on that just spells and activation costs.

Just a few of the avatars you can pump mana into are Arcanis, Ashling, Braids, Figure of Destiny, Master of the Wild Hunt, Mirror Entity, Momir, and Peacekeeper... whew!  Anyway get 4 of these if you have any interest in vanguard.

Energy Field

Don't be fooled: this card does not combo with Planar Void.  Or Leyline of the Void.

It does (sort of) combo in the late game with Forbidden Crypt or Yawgmoth's Agenda, but really the best use for this card is just to protect your permanents, and not cast any instants or sorceries.  Which makes this card pretty bad, but that's the kind of card I like!

The avatar I want to pair with this the most is actually Tradewind Rider.  If one of your permanents is about to get destroyed, pay 3 and bounce it to your hand!  Is it an unbreakable lock, of course not, but it will at least exasperate your opponent for a few damage-free turns.  While also returning his own permanents, or dropping his life total.

Veiled Crocodile

Yeah, I said it.  Veiled Crocodile.

Whether we're talking a Lyzolda avatar / Imaginary Pet deck, or any type of Grinning Demon deck, you're quite likely to be turning this guy on, giving you a 4/4 on the (well kind of) cheap.  At least, cheap considering what blue typically gets for this much mana.

I also have a couple of Howltooth Hollow decks he could fit into....

Lurking Evil

A lot of what I said for Flesh Reaver above is true of this guy as well.  He makes you lose so much life as to be generally not worth it in regular Magic, and he's good with the Serra Angel avatar.  But there are a few differences:

1. This guy is not good with the Loxodon Hierarch avatar.  With Reaver you can gain life whenever you want — with this guy, you had better gain it after you turn him on.  In fact, he may even be good with an avatar that starts you at a low life, so his "half" cost will be lower.  Risky, but worth a thought.
2. This guy does make you lose life, not take damage, so the Stuffy Doll avatar is out.
3. He flies, so he's unlikely to be chumped by Llanowar Elves.

All in all, worth a shot.  Just don't forget to activate him during your opponent's end step (barring a compelling reason to do it differently).

Bulwark

I've always had a peculiar fondness for the wisdom-friendly avatars.  And another peculiar fondness for mono-red defensive decks.  Then along comes a card that ties the two together!

Bulwark dealing damage may not be a guarantee in formats with 7-card hands, but when you're packing a Squee avatar (+3 hand size!), it becomes much closer to one.  Even if your opponent isn't playing with the –2 hand size of Reaper King.

Argothian Wurm

We already have Shivan Wumpus online, and for the most part, everything that's true of one is true of the other.  Both go great with avatars like Orcish Squatters, Hermit Druid, and Mayael the Anima. But there at least two key differences:

Only one of these creatures is in the color of acceleration.

And only one of them can be cast on the first turn using only Crystal Vein and an Eladamri avatar.

Endless Wurm

Even when he's not wearing a Rancor, he's still quite a force.

There aren't any specifically enchantment-friendly avatars, but there are sure a few avatars that combo well with certain enchantments.  You were probably already running Hatching Plans in your Loxodon avatar deck, so why not put in this guy too?

There are also more cantrip and EtB enchantments than ever, giving this guy plenty of food that won't cause you too much grief.  And don't forget that he's in the same set as Argothian Enchantress.

Hidden Herd

Of all the Hidden cards, this is one of the few that's safe to maindeck in the casual room while still being efficient.

Tournament players can run Hidden Gibbons and Hidden Guerrillas without a care in the world, but we casual players can't be so confident.  Still, even in the casual room, it's rare to see anyone who doesn't have a few nonbasics.  And with stats this efficient, you often won't even mind if he takes a turn or two to switch on.

Phyrexian Tower

Between avatars who gives you tokens and avatars who encourage you to sacrifice creatures, this should have no trouble finding a home.

I already have designs on this for a Grinning Demon deck.  And it's one of the very few cards to make me even consider using the Malfegor avatar.

It doesn't even enter the battlefield tapped!

I can't tell you how tired I am of having my only Toshiro Umezawa get killed, then having to sit there waiting to draw another one before I can reuse all of those instants in my graveyard.  Unearth offers easily the most efficient way to do this.

What am I supposed to do, pay 3B for Zombify?  (Or 1BBB for Raise Dead and a recast?)

It even cycles!  I would have played with it anyway.

Sigil of Sleep

If you've been playing vanguard long enough, you probably have a few decks centered on getting your creatures unblocked.  Between the Higure, Rith, and Maelstrom Archangel avatars, you have ample enough reason to.  And there's only so many times you can play that 8x Curiosity / Keen Sense deck.  Sigil of Sleep offers you an alternate route.

And also a reason to dust off that old Ninjas deck you used to play.

Reckless Abandon

There are a lot of similar cards already online.  Fling, Goblin Grenade, Lightning Axe, Fireblast, and so on.  But none do quite what Reckless Abandon does, which in more than a few Higure avatar decks is very worth doing.

It's also better next to your Rukh Egg than any of those other cards I mentioned!

Scent of Cinder

Wisdom decks... defensive red decks... what was I saying earlier?

Even if this is "only" X=4, it's quite a good deal.  And if you play this in the right deck, it will almost always be more than X=4.

The information you're giving your opponent could be crippling in a tournament match, but I'm a casual player — what care have I for tournament matches?

Rofellos's Gift

This is the only card on my list I'll be saying this for, but I have no idea how to use this card.  I never did.  (A quick Google search for "4 Rofellos's Gift" will show you that not a lot of other people do, either.  Only 1 actual deck appears and, no offense to its maker, but it doesn't exactly excite me.)

I used to stare at my copies of these for great stretches of time, thinking there has to be SOME way to abuse this!  I still think there is.  I still haven't found it though.

I remain confident, however, that a severely discounted Skull of Orm has to be playable somehow.  It has to be.  (If you have any ideas, please leave them in the comments!)

Thran Dynamo

The Orcish Squatters and Hermit Druid avatars double your mana, but double still wasn't enough for me.  I would contrive ways to get even more mana out of them, usually relying on things like Blinkmoth Urn, Gauntlet of Power, or Mirari's Wake.  All of which are five mana.  There just didn't seem to be a good 4-mana solution (what was I going to do, power out a Sisay's Ring?).  But Thran Dynamo might be just what I was looking for.

Sure, it's not as powerful as Blinkmoth Urn, but it also doesn't rely on a turn one Signet — or any other card — to come down on Turn Two.  It only needs itself and the avatar.  Just remember to draw first with Orcish Squatters.

Opalescence

Don't bring your tournament-caliber deck with this, Replenish, and Academy Rector into the casual room.  But do bring your janky deck using this with stuff like Aurification or Spirit Mirror.

Unfortunately, I can't make an enchantment version of my Braids avatar / March of the Machines deck, since Braid doesn't put enchantments into play (a design choice I can't imagine the reason for), but I'm sure I'll figure something out by the time this card comes online.

Attrition

I hope I'm not sounding like a broken record, but "this combos with the Erhnam avatar, the Teysa avatar, and the Fallen Angel avatar.  And with Rukh Egg."

If nothing else, this is almost always a better deal than Hecatomb.  And I have crammed Hecatomb into more than a few decks.

Covetous Dragon

For all of the enchantment-friendly avatars that don't exist, there are sure a lot of artifact-friendly ones that do.  Bosh, Stonehewer Giant, and Raksha should all ensure this guy's survival.  As should the many artifact-heavy decks for virtually any other avatar.

Repercussion

Remember the days of playing Ragged Veins in your Pyrohemia and Ashling avatar decks?

For one mana more, you have a card that not only affects multiple creatures, but is way more permanent.

It affects your creatures too, of course, but that's nothing some creative deckbuilding can't handle.