I was live for the Thiago Alves one too...it was like everyone had got as excited as they could...Boomer was next to me bouncing up and down...and then he just dropped into his chair and said "oh no" you could see him deflate like a balloon
Personally, I think that Hughes/Penn (the first one) is the biggest upset of all time, because Hughes was in his first Reign, he had plowed through everyone...and BJ Penn was pretty much a platea. He'd been tooted as one of the best up and comers...but couldnt beat Pulver, nor Uno for the title at Lightweight...and got the Welterweight showdown as a gift from the management.
Noone expected him to win.
I think after that Jens/Penn 1 is the second biggest...for almost the same reasons reversed. BJ Penn was the unstoppable up and comer, and he just seemed destined to win...even two rounds into the fight he seamed destined to win. It was a suprise that Jens managed to defend his Title.
After that its got to be the first BJ Penn Frankie Edgar fight...again, for very similar reasons as number one. Penn was indestructable at Lightweight after the division reformed...he not only beat everyone, but he finished them all, in one of the best divisions. His pure skill was simply unmatched...he toyed with them and then destroyed them...and then Frankie Edgar...who isnt even someone special...caught Penn...Twice?? unheard of...absolutely unheard of.
Then I would put the Gonzaga/Crocop fight...coz it was so shocking, all of us present though Mirko had been killed or something. It was also bitterly ironic because of the trademark move that crocop likes to use.
After that...maybe the Lauzon/Pulver match. The returning Champion, and the tin can that turned out to be a right can of beans...I remember that because that was one of the first events I stayed up for. I was talking to Miss Jenn at the time...we spoke for hours after that coz I was litterally inconsolable...I hadnt cried so much in years