#4 Sami Zayn
Sami Zayn has given his heart and soul to WWE over the last couple years, and has he gotten very little in return - from the fans or the company. That's not to say that neither aren't grateful for Zyan's talent. He was likely just a bland babyface for such a long time, and needed to turn heel to have his true potential realized.
In all honesty, Sami Zayn's new gimmick of shooting from the hip and airing out his grievances is insanely genius. It is also something that has quickly raised the stock of the former NXT Champion and given him a much better chance at success. He's been heading in that direction ever since his initial heel turn at last year's Hell In a Cell - a move that was sadly derailed with his recent injury.
If nothing else, Zayn is another one of those diamond in the rough situations that the company needs to capitalize on. Of course, they are going to first have to take him off of the losing streak he is currently on and stop using him to put over other stars, but the future looks extremely bright once they do that.