Hearthpwn

This is my 2015 Christmas deck and the theme is having no idea what you're going to get each game. This is accomplished with a mixture of card steal and discovery, along with some random summoning. This deck will almost certainly lose against any real form of aggro and is not at all well balanced, lacking AOE removal, silence and necessary buffing tools. That said, when it does work, it's hilarious fun and will give you plenty of surprises. It's also the best way yet to "play your opponents deck", utilizing all the new steal cards available in the latest expansions.

Generally in my experience you should be looking for early discovery in your opening hand. Museum Curator and Jewelled Scarab are your must-keeps and will give you the early momentum and choice you need to stay in the game. Museum Curator almost constantly gives you Dark Cultist as an option, due to Discovery cards having a much higher chance of presenting a class card than a neutral, so turn 2 curator into turn 3 cultist will give you some great power on the board early on. In a pinch, a convert can come in handy if you end up with an awful opening hand, at least you can copy one of their minions and have a card you can play. Generally though I will mulligan Convert if I have other 1-3 mana cards in my opening hand, since Convert tends to be much more powerful later in the game when you have more mana to play with and the opponent is dropping his high impact minions.

Early Mind visions and Thoughtsteals will give you options, though if you can do something else, considering holding onto mind vision for mid-game for a chance at higher mana cards. Where possible, try to save Entomb for high impact deathrattle minions, since Entomb is hard removal that doesn't trigger deathrattle, a rare commodity. Finally if I had any other advice, its don't be afraid to drop MCtech on the board turn 2 or 3. Yes his battlecry is amazing, but it's very situational and you are much better off with a 3/3 on the board at that time than losing control of the board and likely the game. The deck has plenty other steal cards to play with.

To make this deck more viable, while sacrificing the purity of the gimmick, I'd include AOE, shadow words and Velens Chosen. To ramp up the insanity even further, try adding a Brann Bronzebeard to the mix for double discoveries and Cabal steals.