Hearthpwn

Messing about again, this time with Hakkar, hoping to queue into Mecha'thun decks. [UPDATE: This deck kind of works.  It's not Tier 1 or Tier 2, but I'm having a surprising amount of success with it in the Pirate Warrior matchup.]

The idea is to play Flark's Boom-Zooka, to pull both Mo'arg Forgefiends and Hakkar, the Soulflayer from the deck, and put them into the deathrattle pool.  Then, keep reviving them with Nine Lives, Jewel of N'Zoth, and ultimately, Zul'jin.

To manage the Corrupted Blood that are shuffled into the deck, Sphere of Sapience can send a Blood to the bottom of your deck, and Deathstalker Rexxar and Rhok'delar can keep the hand full with generated cards, until all Bloods have been milled.  [UPDATE: Rhok' is cuttable.  So is Rinling's Rifle.  Trade them for Spring the Trap, or Resizing Pouch, or something else which can generate cards and be repeated by Zul'Jin.]

Let's talk about Sphere of Sapience a bit more.  This deck is built around Boom-Zooka, and Sphere makes the 'Zooka a lot more reliable than it would otherwise be.  In the early turns of the game, use the Sphere to send minions to the bottom of the deck.  In the middle turns of the game, when you're digging for the 'Zooka, you can send secrets to the bottom of the deck, too... because can draw them with Dun Baldar Bunker.  And the more secrets you pull from your deck with Bunker, the better the chance that Sphere, or Tracking, will find 'Zooka.  (Do try to keep one charge on the Sphere for sending a Blood to the bottom, however.)

One more point about Corrupted Blood: sometimes, you want to shuffle more of them into your deck, to hold off on fatigue.  Because while your hand is full, you take no damage from the Blood, and you don't draw into fatigue damage, either, if your deck is otherwise empty.  This has been a surprisingly useful tactic in grindy matchups, after I've drawn way more cards than my opponent, and I'm waiting for their Bloods to be drawn.

Don't expect to beat aggro decks, but if you can string the right secrets into Beaststalker Tavish in the mid-game, you might be able to stall long enough to play the expensive cards.

Cards to keep in the mulligan are Flark's, Sphere, Bunker, and possibly an Explosive Trap or Wandering Monster, if the opponent is aggressive.  I might also keep Tracking, if I really need a good turn 2 play, but ideally it's best played in the mid-to-late game to find 'Zooka, or Jewel.