#5 Uriah Hall
Ever since his tenure on The Ultimate Fighter, Uriah Hall has been tipped for greatness in the UFC. Whilst he hasn't exactly lived up to the hype as of yet, Hall is still one of the most imposing figures we've seen in mixed martial arts for quite a long time. He comes across as a nice guy behind the scenes, but it's his ability to flick the switch that makes him dangerous.
As The Undertaker, Hall's sinister walks to the ring would likely send chills down the spine of the WWE Universe week in and week out. He'd be a different kind of animal as he can finish a match at any given moment, all the while being entranced by his demeanour and the way he carries himself. It seems odd and a little bit out there, but with a bit of tweaking Hall could definitely make it work.