Rorion Gracie
You might see Rorion Gracie's name on this site and ask yourself "Has Rorion Gracie ever fought MMA?" Well, that depends on how you define MMA. I don't believe he's ever fought a professional or sanctioned MMA fight, but nonetheless, he is a legend of the sport, if for no other reason than he is responsible for starting the Ultimate Fighting Championship.
However, Rorion is a deadly fighter as well. As the oldest son of Helio Gracie, he is well trained in Brazilian Jiu-jitsu, being one of only a very few people in the world to hold a 9th degree black belt in the art. Rorion received that promotion on October 27th, 2003 from his father Helio.
Rorion has indeed used his martial art in combat on several occasions.
