2: Fel Reaver
As is the case with most cards that are completely broken, at least half of the opinions I read about Fel Reaver were that it was completely unplayable. Just so we understand each other-Fel Reaver is an 8/8 for 5. Removing the top 9 cards of your deck won't affect the quality of your draws on average, and is only a drawback if you literally lose because of fatigue. Given that the drawback on Fel Reaver basically doesn't exist in 99% of games, I'd say that this 5 mana 8/8 is a pretty efficient creature. This is the best card in the set for aggressive decks, and the first time somebody curves Fel Reaver into Savannah Highmane against you I think you'll agree.