A lot of people won't agree but I can't believe I forgot these guys
Mat Hoffman
Tony Hawk
Kelly Slater
These dudes are living legends and aren't appreciated enough outside of their sports. A lot of people don't even consider their sports, sports.
Also, I used to bowl a lot growing up but even I don't consider bowling a sport, but Walter Ray Williams Jr. is a beast. If bowling is considered a sport, it is definitely one of the hardest to be consistently excellent.