Two: Flamewaker
This is my personal least favorite card in Hearthstone. People have joked that Flamewaker’s text reads: “if this card is in play on your next turn, win the game,” and I believe that is far too close to the truth. Flamewaker backed by a Mage’s arsenal of spells represents the ability to clear your board infinitely while pushing incredible face damage. It also comes out on turn three, before most decks can easily deal four damage. Playing against someone who has Flamewaker + Coin + Arcane Missiles on turn three feels like an almost unwinnable situation to be against, and it’s one that happens far too often with the Mage’s arsenal of low cost spells.