I'll start.
Fedor Emelianenko
Close second: GSP
I'll start.
Fedor Emelianenko
Close second: GSP
The two best ones in MMA,Wanderlei silva and Chuck lidell :)
GSP! GO CANADA!
other than that, anderson silva, he seems almost untouchable no matter what weight class he is in
Brock Lesner and St. Pierre
Oh I have too many favorites to limit it to one. Fedor Emelianenko, Antonio Rodrigo Nogueira, Wanderlei Silva, Mauricio "Shogun" Rua, Yoshihiro Akiyama, Dong Sik Yoon, Ronaldo "Jacare" Souza, GSP, Karo Parisyan, Dong Hyun Kim, BJ Penn, Tatsuya Kawajiri, Chan Sung Jung, Urijah Faber, Kid Yamamoto, Rambaa "M16" Somdet. Those are just the ones I can think of off the top of my head. Have many more.
Fedor has got to be up there , along with GSP and silva
but myt favs to watch K-1 buakow por pramuk, and igor vovchanchin from old days. too many too list now that i think off it :)