1) Fedor vs Bigfoot - Fedor's loss to Werdum could have easily been passed off as Fedor's over-aggression and Werdum catching a "lucky" submission. But Fedor was busted up by Bigfoot, and the fight was stopped. People walked away from that fight knowing that Fedor's reign was over.
2) Shogun vs Machida I - The overwhelming majority of the MMA community felt like Shogun exposed some serious holes in Machida's game, and that he was robbed of the win. The Machida era ended shortly after it began with this fight, even if he still got to hang onto the belt until Shogun vs Machida II.
3) CroCop vs Gonzaga - Those of us who have been watching MMA for many years remember the hype surrounding Mirko as he developed his name in Pride. Sure, he was knocked out by Randleman. But a lot of that felt very much like a fluke -- Randleman tricked Mirko at the start of the fight and landed a devastating bomb on him. But when Gonzaga KOed Mirko , there was nothing "lucky" about it. He dominated him on the ground, then knocked his head off. No one really feared Mirko after that.
4) Jones vs Gus - Gus made Jones look very beatable. He hit him, controlled him and to the eyes of many, won the fight. Prior to this fight, Jones never really looked beatable -- he always managed to get out of range of any damage.
5) Hughs vs Penn I - Seriously, this is one of those fights that made BJ Penn a legend. Hughs was dominant, and BJ Penn submitted him beautifully.
6) Couture vs Liddell I - Couture boxed Chuck up and dropped him on his head, repeatedly. Prior to that, Liddell was just knocking guys around and knocking guys out.
7) Couture vs Belfort I - Vitor sort of gets a pass because of his personal issues. But Couture's constant pressure showed that Vitor will wilt at some point. Vitor carried that reputation with him for years (deservedly).
8) Shogun vs Jones - We've never seen Shogun get beat up before, and Jones just dominated him. Prior to that fight, Shogun's losses all seemed very "once in a lifetime."
9) Bowles vs Torres - Torres had a huge win streak heading into the fight, and was a consensus top five P4P. Bowles knocked him out cold. After that, both men went on a bit of a skid -- but Torres was one of the most dramatic.
10) Weidman vs Silva II - In their first fight, it really looked like Silva's antics just cost him, and he was hit with a hard shot. Anyone can be dropped, right? But in the second fight, Silva put the plume on Weidman, and Weidman stood with it and dropped Silva hard. I think everyone seen Silva's lights flicker on that one. And then Silva's leg literally broke against Weidman's. I don't think any top-tier fighter ever looked so broken after only two fights. Even Mirko and Wand came back to win after losing.
Always A Fan: Fedor, Henderson, Mirko, Penn and Shogun