5. Anderson Silva
You can't have any UFC list without Anderson Silva on it - the greatest MMA fighter of all time. WWE could use Silva much in the same way that they used Floyd Mayweather, bring him in for one big promoted bout against a big guy. Silva with his deadly kicks and teasing ring style would be able to entertain hugely in such a WWE match. Having recently dropped the UFC Middleweight title after a Seven year reign in a losing effort that cost him his 17 fight undefeated streak, Silva may well be thinking of pastures new after his UFC fight contract runs out. He is a big star, the first MMA star to get deals with Nike and other big sponsors, WWE would be aware of the brand potential of bringing Anderson Silva in for a shot. Silva of course pretends he can't speak English so promos are out if he came to WWE. But his ring style speaks for itself, sick kicks, strong wrestling, submission techniques - Silva can excite. He is also very Muhamad Ali in the way he dances around his opponents, he is a provoker of people and could be a great wrestling heel in his work.