Hearthpwn

I've been playing this as my primary ladder deck, with only minor alterations along the way, for the past two seasons. And although Discard Zoo has become more refined and settled over that time, I haven't seen any that make the particular set of decisions that this one does. I wanted to update the description here to describe the reasoning behind these inclusions, since I believe they're tailored well to the current meta in the context of an aggressive gameplan.

I think of the deck as consisting of a few functional pieces:

1. The Discard Package

Soulfire, Doomguard, Malchezaar's Imp, and Silverware Golem are all standard at this point in Discard builds. Many also include Darkshire Librarian for additional cycle, functioning essentially as a 3/2 Loot Hoarder with the additional possibility of generating value from the Golems and Imps. Librarian is an excellent target for PO's that would otherwise be discarded, providing both a huge damage hit as well as mitigating card disadvantage and facilitating cycle.

While typical Discard Zoo builds include Darkshire Councilman, this one substitutes Tiny Knight of Evil instead as the buff option. While Councilman's 5 toughness makes it stickier when initially played, it typically takes several turns to gain value, and since this deck's ideal hand size is 1 or 2 and includes mostly 1- and 2-drops, Councilman comes at a part of the curve where its fuel is already mostly expended. This deck's game plan of getting damage to the board early and keeping hand size small to control the discard effect means that Councilman is, in this deck's playstyle, slow to grow once it's played.

Tiny Knight of Evil is an instant removal target when it hits the board, but if played as a lead-up to a Doomguard turn, is an enormous threat that can often become a 5/4 attacking if it is not immediately taken care of. The fact that its buff also increases health can be very helpful against AoE or direct damage removal methods, and if grown over more than one turn, it can either do serious face damage or take down high-health taunts, leaving the deck's stickier minions undamaged.

The inclusion of Tiny Knight of Evil means that the single copy of Succubus is potentially useful to build an extremely threatening board as early as turn 2. Succubus must be used very carefully in this deck, but with the right draw can be a great early minion. Obviously the main thing to take care of is that you do everything possible to avoid discarding a Doomguard. Later, with an empty hand, Succubus's drawback vanishes, and it delivers more stats for 2 mana than other minions at that cost. At that stage of the game, it can additionally help pull a free Golem and/or cycle with an Imp to dig for game-ending damage. Failing all else, it provides fuel to be discarded, generating value from Imps and Tiny Knights from hand.

2. Same old Zoo

The strength of Zoo in terms of early high-value minions remains the skeleton of this deck. Flame Imp provides great early tempo; late, when the 3 damage may be too high a price to pay for a minion that is easy to remove at that stage, it can like Succubus provide value as discard fuel. Voidwalker remains an exceptional minion: Cheap taunt in an aggressive deck can provide a huge tempo advantage, and 3 health makes it a sticky 1-drop that can survive a Maelstrom Portal or even the occasional Lightning Storm. Imp Gang Boss is the epitome of a sticky minion, excellent against Mage and providing tokens for Abusive or PO buffs. Possessed Villager continues the stickiness theme, providing a buff target that is a waste of your opponent's early removal. Dark Peddler's ability to replace itself, allow you to dig for a third Soulfire or PO or Abusive (not to mention the many other situationally useful 1-cost cards, from Young Priestess to Mortal Coil to charge, stealth, or buff minions...), and serve as a target for PO or Abusive for early removal makes it as always excellent.

The omission of two particular Zoo staples--Direwolf Alpha and Defender of Argus--is in line with the deck's gameplan. While both are very useful minions in Zoo's typical value approach, both are primarily removal/defensive options that rely on having minions on board in order to generate that value. The advent of Shaman in the meta, and the widespread understanding that the way to hamstring Zoo is to keep its board clear or mostly clear, makes these two minions' utility situational. For a deck that is very often drawing for answers, neither card is enough of a threat in its own right to merit inclusion.

3. Tech

Conventional builds of Discard Zoo are already effective in the meta primarily due to their favorable matchups against Hunter, Mage, and Druid. Its main drawback is vulnerability to Shaman, so this build includes two measures to improve that matchup. Argent Horserider is an exceptional totem-killer, allowing you to keep the Shaman from building early board while also keeping its shield intact, giving it additional stickiness against Shaman AoE. It is very useful for chip damage on big taunts, and perfect for carrying an Abusive buff. It is a great minion for proc'ing traps (Freezing, Explosive, and Snipe) and can give a little extra surprise damage to help pop a block or deliver lethal against Freeze Mage. The fact that your opponent does not expect this card to be in the deck makes it more value beyond even these aspects, as most players are in the habit of having a turn to respond to any minion Zoo plays except for Doomguard.

Speaking of surprises, Demonwrath is included explicitly as anti-Shaman tech. Like Succubus, this is a card that is only situationally useful and may in many matchups simply become discard fuel. However, the ability to wipe a Shaman opponent's board the turn before a Thunder Bluff or Bloodlust can be just the tempo swing needed to sustain pressure against Shaman and take the game. The element of surprise means that your opponent will not think twice about overextending into this card. Certainly, though, it must be used judiciously, as your own deck does include many non-Demon minions, meaning that you must always calculate cost/benefit and adapt your play to the game situation.

In summary:

The deck's playstyle differs a bit from conventional Zoo, and even slightly from the other Discard Zoos you may see on ladder. It is more oriented on aggression and speed, less on board control and value trading, than its brethren. This isn't to say that it must be played as a face deck: It has most often a conventional Zoo opening, and it remains important to keep the board clear on early turns, but the primary purpose of that tactic is to keep the way open to deliver devastating hits very early in the game, and end it quickly.