I really like watching MMA, but I don't particularly have a favorite. I guess if I was gonna pick someone it would be Clay Guida. I like the way he takes it to people. I also like the way the Diaz brothers fight.
Good question, because there are several I think stand out right now for me. Georges St. Pierre, Lyoto Machida and Anderson Silva. Beyond UFC, still Rickson Gracie, Gegard Mousasi (only 24 years old!), probably Fedor Emelianenko.
Silva is the favorite in my house. I rarely watch anymore. Got banned. There was a guy who I guess was sponsored by Condom Deptot or something and Condom depot was in big letters all over his butt and I couldn't stop laughing, so now I am sort of unwelcome in the frontroom during UFC. :-)
I enjoy watching Brock Lesnar fight a lot. He takes a lot of slack because of his WWE background, but this guy is a freak of nature. He is one of the most gifted athletes I've ever seen and genetically he looks like a super hero. Can't wait to see how he grows over the next few years.
I think everyone has great answers. Each fighter named is great in their own right. I even despise some of the fighters personalities (Ken Shamrock, Brock Lesnar, etc.) but there is no denying their capabilities.
How about outside the UFC? In any promotion? Gina Carano.
I absolutely adore this chick. She's a wonderful role model for little girls, too.
As far as men go, I totally agree with the earlier post of Mousasi. He is a BEAST!