Still the most viewed fight in MMA history.
Had Kimbo beat Ken Shamrock (or Petruzelli) that night, he would not only still be the face of MMA, but alot of talk post UFC 100 would be centered around Brock vs. Kimbo, not Brock vs. Fedor. Brock/Kimbo would have been the biggest money fight in MMA history, and would threaten all of the boxing records.
Also, EliteXC would still exist, Strikeforce would still be a regional promotion, and Affliction may have never gotten into the fight game.
All because Ken banged his head.