The best natural athletic talent I ever saw was RJJ. The best natural boxing talent I ever saw was James Toney. The best combination of the two is Mayweather.
Well, in some sense I would say this is a style of fighting only he can pull off with success I guess that would be a natural talent.
Why are people mentioning Amir Khan? It's obviously there opinion, but I wouldn't call it natural talent what he possesses. Isn't that why he moved to America so he could learn from Roach? You obviously still need to learn new things when you have natural talent, but I wouldn't say his natural abilties were up there with Jones, Mayweather, and Toney...
Roy Jones did things in the ring no fighter has done and was the best p4p for a decade. Reflexes, speed, movement unorthodox style and power its not even close.
Naseem Hamed is a guy I am suprised to see mentioned so little, he barely trained and he would still dance into the ring, front flip over the ropes, toy with you and knock you out. Unless your Barrera. Amazing reflexes and punching power, not to mention some nice dancing skills. Some of the more obvious choices are... James Toney Roy Jones Jr. Floyd Mayweather Jr. Mike Tyson