Man thats a tough one...it seems we did this thread before..I looked but couldn't find it anyway here are some by fighter

Hughes vs Trigg I/II, Newton, GSP I/II,
Penn vs Gomi, Hughes I/II, Gracie
Gomi vs Diaz, Sakurai, Pulver
Franklin vs Tanner II, Silva
Henderson vs Silva I/II, Big Nog, Lil Nog
Wanderlei vs Belfort, Sakuraba, Arona, Mezger, Jackson, Fujita, Crocop
Quinton Jackson vs Arona, Chuck, Randleman, Shogun, Lindland
Arona vs Sokoudju, Shogun, Overeem
Shogun vs Lil Nog
Ortiz vs Couture, Chuck, Silva, Mezger II, Frank Shamrock
Chuck vs Babalu, Couture 1-3, Randleman, Overeem, Mezger
Fedor vs Hunt, Fujita, Crocop, Noguiera, Randleman
CroCop vs Noguiera, Barnett, Hunt, Randleman, Yoshida, Gonzaga
Big Nog vs Ricco Rodriguez, Barnett, Khartinov, Coleman
Mark Coleman vs Goodrige, Frye, Severn, Smith, Williams
Royce Gracie vs all of his early UFC and Sakuraba

I know this is alot and by no means is it all, but these are some of the biggest players in MMA over the years...I'm sure I'm missing some big ones though