#3 Sami Zayn

Sami Zayn just made his return from a 10-month injury hiatus on this past WWE RAW, and didn't waste any time at all getting back to his heel form, and without KO by his side this time, the sky is the limit for Zayn.
Sure, he's never going to have the look that Vince McMahon desires in a top heel, but not everyone needs to be at the top of the industry, and Zayn has more than enough talent and charisma to be a main event player for years to come.
Sami made his mark as a heel during his last run, and nothing would be more heelish than winning Money in the Bank and cashing it in on an unsuspecting Champion. We aren't saying that he should cash it in on Kofi Kingston at some point, but if he were to do so, with that and the combination of his charisma and pure smug attitude as a heel, he'd be the most hated man in the entire company, so it's worth a shot.