There are tons of MMA matches that stand out in my memory. Some more recent, others older.
Bob Sapp Vs Minotauro (Pride FC Dynamite) is one of them, as Nogueira was able to withstand Sapp's strength and brutality, eventually proving that stamina goes a long way towards winning, and armbaring the guy.
Forrest Griffin Vs Stephan Bonnar on the TUF 1 Finale (UFC) was another, as these two guys stood toe to toe for 3 rounds, banging their heads out. No clear victor emerged.
Minotauro Vs Cro-Cop (Pride FC). Mirko looked devastating and clearly punished Nogueira for an entire round, but Minotauro eventually was able to come back.
Pele Vs Carlos Newton (Pride FC) had a fast pace and that "grappler vs striker classic" feel to it. Pele caught Newton and everything seemed finished, but Newton was able to turn things around with a slick submission.
I could go on and on. But a moment for what is my all-time favorite match; at least, of those I've seen so far.
I've never liked Frank Trigg. He's too cocky, likes too mouth off about things that have absolutely nothing to do with the actual match. But he's a terrific wrestler, I'll give him that. Matt Hughes had beaten him, in a highly anticipated match, at UFC 45. Before that match, Trigg was basically an almost untouchable fighter, very dominant, hailing from the RAW Academy (training partner of BIG Tom Erikson). And Hughes was the welterweight champion. Hughes had won the belt in a highly controversial match against Carlos "The Ronin" Newton, who had beaten Hughes' mentor and coach, Pat Miletich. Hughes was out, but so was Newton; so the belt was awarded to Hughes in what is arguably one of the most controversial matches ever. Hughes had to prove that the belt belonged to him; so he went out and beat everyone laid in front of him, pure dominance: Hayato "Mach" Sakurai, Carlos Newton (in the UK; Hughes brutally devastated Newton in a position that is sometimes referred to as the "Hughes-Newton position"), Gil Castillo (a Cesar Gracie fighter), Sean Sherk (who was unbeaten before that match). Then came Trigg, at UFC 45. In what was basically a wrestling match, Hughes capitalized on a crucial mistake and secured a STANDING rear-naked choke.
In the following title defense, Hughes lost his belt. He was rear-naked choked by the awesome BJ Penn. Penn and the UFC had a quarrel, so Penn eventually left (he later came back), the belt being rendered vacant. Hughes was immediately looked upon as a top contender for the vacant title. He beat Renato "Charuto" Veríssimo (the BJJ coach of BJ Penn) and regained his title in a great match against up-and-comer canadian sensation Georges St. Pierre.
After his loss against Hughes, Trigg went back to the drawing board. And what a board it was. Trigg pummeled Dennis "Superman" Hallman, the only man ever to had beaten Hughes twice. After that, he also took care of Renato Veríssimo.
The match was set. Hughes would defend his belt, in a rematch, against Frank Trigg. UFC 52 was the chosen stage.
Trigg had some very nasty things to say about Hughes - and Matt's family - in the build-up to the match. Hughes replied. Trigg pushed the verbal attacks some more, Hughes replied.
It finally arrived, a much anticipated (re)match. When both fighters were being presented in the octagon, Trigg wasn't looking at Hughes. When they came to the center, to hear the referee's instructions, Trigg leaned forward, almost kissing Hughes (but in a menacing way, that is!). Matt shoved him and Trigg blew a kiss. It couldn't get any better. But it did.
As the match started, they got into a clinch. Trigg kneed Hughes in the groin (illegal blow). Matt was shook up and looked at the referee for help, but he didn't see the illegal blow. So Trigg seized momentum and pounded on a rocked Matt Hughes. The fight went to the ground, and Trigg engaged in great ground 'n pound. Hughes was hurt... badly; he then gave his back and Trigg worked for the rear-naked choke. As he secured it, Matt's face was between red and purple, I kid you not. At that time I thought "Matt's finished, Trigg is the new champ... this sucks!".
Hughes was able to escape the choke (how? no idea), recovered his composure and PICKED Frank Trigg UP ON HIS SHOULDERS. He slammed Trigg hard. The reaction from the crowd was AMAZING. And rightfully so. Hughes then proceeded to deliver some ground 'n pound of his own, and Trigg gave his back. Matt applied the rear-naked choke and Trigg was forced to tap out. Matt Hughes was still champion after an incredible match and a near impossible comeback.
Great, great match.