White Weenie was a tier 1 deck at the end of last season, with Craig Wescoe finishing 5th at Worlds with a Boros version powered by Slayer's Stronghold and Sublime Archangel. However, when Innistrad rotated, the archetype lost some key cards and has been a fringe deck in Theros block so far.
Why play White Weenie now?
The current meta is centred around control and midrange decks, so very few decks are set up to beat small aggro (eg it's rare that black decks have Drown in Sorrow in the sideboard at the moment). Also several of the best cards in the forthcoming Journey to Nyx set make this archetype more powerful, most notably Athreos, the B/W god, but also some some good utility cards like Banishing Light, plus anti-god tech in Decide and Godsend.
What's with the black splash?
The black splash is necessary to play thoughtseize,
which is the most efficient way to deal with sweepers. It also lets you play Xathrid Necromancer, a powerful tool against control and midrange decks that rely on 1-4-1 removal (eg MBD). Finally, it also gives access to the full black removal suite, to give more options for dealing with troublesome cards such as Stormbreath Dragon and Polukranos.
Sample Decks
Pat Cox (44th place at GP Cincinnati, 23rd Mar 2014)
Ben Stark (4th place at GP Dallas, 7th Dec 2013)
The Cards
Main Deck
1 drops:
Soldier of the Pantheon Good on offence and defence. Immune to Azorius charm and detention sphere. Can't be blocked by Reckoner or Frostburn Weird. Auto 4-of in any white aggro deck.
Dryad Militant 2/1 for 1. Not very exciting, but gets the
job done. G in the casting cost can be a liability against Mono-U because of Tidebinder Mage. One downside is that she is not human, so doesn't trigger Xathrid Necromancer. This is often the card that gets sideboarded out, and could see it getting cut post JOU.
Boros Elite I was initially very sceptical about this card (bad T1 play, bad on defence, etc etc), but after finally acquiring some mutavaults on MTGO and testing with him, I actually think he's fine (and currently an auto 4-of). You have a lot of ways to ramp in to batallion (Precinct Captain, Brimaz, Mutavault) and in games where you are swinging for lethal with Brave, he will almost always be a 3/3.
2 drops:
Precinct Captain The best 2 drop against aggro(defence) and control (let's you apply pressure, without having to commit all your team to the battlefield and risk a verdict). Conversely one of the worst against G/R (as Sylvan Caryathid stonewalls him). He's an auto-
include as things stand and gets better with Athreos, as he generates 2 devotion on his own.
Daring Skyjack Another card I was sceptical about, but is actually one of the most solid cards in the deck. The evasion is relevant surpisingly often, he can attack in to Sylvan Caryathid, trades with x/3s and triggers Xathrid Necromancer. Auto 4-of.
Imposing Sovereign This card ranges from game-winning to terrible, depending on the board state. Having your opponents blocker come down tapped can sometimes let you swing in for lethal. She also completely nullifies Whip of Erebos and makes it harder for Xenagos or Elspeth to land safely. She also makes racing red aggro easier, as screws up all their haste guys and stops G/W decks from flashing in surprise blockers. She is bad in multiples though and is a fairly weak body when you are trying to kill off a Jace for example. Pat Cox advises playing her as a 2-of, which I think is about right.
[card:
db7ud6tz]Spirit of the Labyrinth[/card] A recent addition from BotG. The 3/1 body for 2CMC is respectable and the card-draw limit is occasionally relevant (it's slightly hard to tell how much, as you have no way of knowing if your opponenet is sitting on a RtB or Divination they can't cast). His main downside is that he doesn't trigger Xathrid Necromancer. At the moment I play him as a 1-of, but you could possibly play more in a control-heavy meta (at the expense of Imposing Sovereign, which is better against aggro and midrange).
3 drops:
Brimaz, King of Oreskos The Lion King isn't quite as powerful as initially hyped, however he's still one of the best 3-drops available and shines in certain match-ups (similar to precinct captain, he is great on defence against small aggro and can apply pressure to control without you having to go all-in on board presence). Being a legendary, 3 is probably the correct number to play.
[card]Banisher Priest[/card:
db7ud6tz] The other half of your removal suite. He can be one of your most powerful cards, especially against G/x, but obviously opens you up to big blow-outs if he's removed at an inopportune time. One of the keys to playing White Weenie is knowing when to play him and judging how safe it is to do so without leaving up mana for Brave. It's normally worth leaving in some copies against U/w control to deal with post-board Fiendslayers or Archangels.
Non-creature Spells:
Brave the Elements One of the main reasons to play White Weenie. Protects your guys from spot removal, protects against red sweepers, good combat trick for aggro mirrors and most importantly lets you alpha swing for lethal, all for a bargain 1CMC. Remember that opposing mutavaults can still block your guys, when you are calculating if you can Brave for lethal.
Orzhov Charm Part of your main-deck removal suite alongside Banisher Priest. More versatile than Doom Blade /
Ultimate Price and isn't a completely dead draw against control (as it gets one of your guys back). The life loss can become relevant in aggro mirrors though. 2 feels about the right number to play. May see less play when Banishing Light rotates in with JOU.
Spear of Heliod Filling the role of anthem. Unlike Honour of the Pure, this is legendary, so multiples are bad news. 2-of is about right, almost always a bomb when it comes down. The destroy effect also occasionally comes in handy.
Ajani, Caller of the Pride The jump effect can be game-winning and the +1/+1 counters mean you can tick up a threat to break a board-stall. I actually dislike Ajani in the deck though, as our game plan is to swarm, and he is best when jumping a fatty or powering up a fiendslayer. Pat Cox swears by him however. He should become more playable in the Athreos shell, where he can jump Athreos himself and provides 2 devotion.
Sideboard
nThoughtseize One of the main reasons for the black splash. Thoughtseize is probably the most powerful card in standard. It provides an efficient answer to any card, for this deck your main targets will be sweepers such as Drown in Sorrow, but will also be key against troublesome, hard to remove cards like Blood Baron or Jace. Knowing when to play it key, obviously if your main worry is Blood Baron, then wait until turn 5 on the play, to give yourself the best chance of catching it.
Xathrid Necromancer Some permutations of the deck (Ben Stark's for example) maindeck this card. It's ultimately meta-dependant, as it is strong against control and Mono-Black, but bad against decks that aren't removal heavy, such as Mono-U or G/R. Sequencing is important, especially against mono-black, where you want to get this guy down early, to get you 2-4-1s on their spot removal. That said he's not affected by LBZ, so if you think your opponent has LBZ and
you have this + a single white creature, it's probably better to play the white creature first. I expect this card to be played more once Athreos lands due to the synergy between the two cards.
Fiendslayer Paladin Immense against red aggro, black aggro and burn. Bad in most other match-ups. Remember he dies if he's double-blocked by x/2s.
Dark Betrayal Not much to say, necessary because of the prevalence of Black Decks in the current meta.
Doom Blade Great against G/R, good against non-black aggro. Ultimate price is another option if your meta is particularly black-heavy.
Celestial Flare Not a great card, but does give you outs against Hexproof, Blood Baron, so meta-dependant on whether it's worth a slot or 2.
Glare of Heresy Good against U/x control, great against Selesnya, great in the mirror. Faces competition from Deicide and
Banishing Light though once JOU is live.
Rest in Peace Graveyard strategies are too niche at the moment to play more than 1 of these, but could become more relevant if Pharika proves popular.
Example Decklist (this is what I'm playing on MTGO at the moment, with Xathrid Necromance main deck, as I don't have any Brimaz and only 3 mutavaults, as I'm still grinding tickets for the last one)
[deck=poppa_f's W/b aggro]Creatures:29
4 Boros Elite
2 Dryad Militant
4 Soldier of the Pantheon
4 Daring Skyjek
2 Imposing Sovereign
4 Precinct Captain
1 Spirit of the Labyrinth
4 Banisher Priest
4 Xathrid Necromancer
Spells:8
4 Brave the Elements
2 Orzhov Charm
2 Spear of Heliod
Lands:23
4 Godless Shrine
3 Mutavault
1 Orzhov Guildgate
10 Plains
1 Swamp
4 Temple of Silence
Sideboard:15
3 Dark Betrayal
3 Thoughtseize
2 Celestial Flare
2 Doom Blade
2 Fiendslayer Paladin
2 Glare of Heresy
1 Rest in Peace[/deck]
Sideboard Strategy and
gameplan against the common MTGO decks
Mono-Black Devotion
OUT: 1 Spirit of the Labyrinth, 1 Dryad Militant, 4 Banisher Priest
IN: 3 Thoughtseize, 3 Dark Betrayal
We are very much the beatdown here. Game 1 the plan is to swarm with creatures. Getting Precinct Captain going can be key, as gives you tokens to sac to their demons. I'll normally try and play him on turn 3, so I can keep a mana open for brave. Game 2 the plan is basically the same, but we have thoughtseize as a pre-emptive answer to Drown in Sorrow and LBZ. If possible, try and play out all your white creatures by turn 3, to avoid being 2-4-1'd by LBZ.
U/w control
OUT: 2 Orzhov Charm, 3 Brave the Elements
IN: 3 Thoughtseize, 2 Glare of Heresy
Game 1 they key is to try and resolve a Necromancer before they verdict. An early Precinct Captain can allow you to apply pressure, while holding some creatures back in case of a board wipe. Game 2 the plan is the same, except you have thoughtseize to try and strip any Verdicts out.
Remember to wait until turn 3 before playing your thoughtseize to have the best chance of spiking a verdict. Normally if you can blank their first verdict then you will win. Fiendslayer can be annoying in this match-up, but you have 6 outs in your Banisher Priests and Glares
G/R Monsters
OUT: 3 Xathrid Necromancer, 2 Dryad Militant
IN: 2 Doom Blade, 3 Thoughtseize
This is an unfavourable matchup. An early Sylvan Caryathid or Courser is tough to fight through, and cards like Polukranos and Stormbreath Dragon can price you out of attacking and allow their card advantage to grind you down. The best chance is to get enough early damage in that you can finish them off with a Brave. Post JOU, Godsend could be nice sideboard option against them
Mono-U Devotion
OUT: 3 Xathrid Necromancer, 2 Dryad Militant
IN: 2 Doom Blade, 3 Thoughtseize
This is normally quite an easy match-up. You can generally out-race them and your Banisher Priests will normally be genuine 2-4-1s. The biggest problem card is probably
an early Frostburn Weird, as it blocks most of your guys, but you have plenty of ways of removing it, especially post-board. Use thoughtseize here to pre-emptively deal with Frostburn, Thassa etc.
Red Aggro
OUT: 4 Boros Elite
IN: 2 Fiendslayer, 2 Doom Blade
This is a favourable match-up, especially post-board if you find a fiendslayer
Burn
OUT: 2 Orzhov Charm
IN: 2 Fiendslayer Paladin
Similar to Red Aggro, the aim is to land a fiendslayer and race them. Plan B is to resolve a precinct captain with mana open for Brave. Managing your Braves is key to this matchup
Control 
