That list sucks,
Mine would look like this (in no particular order):
Big Nog vs. Bob Sapp- the first time we really got a good look at Nog's chin,heart, and skills.
Anderson Silva vs. Chris Leben- I remember having numerous conversations with various TUF nuthuggers that were saying Leben would kill that nobody. Anderson came,saw, conquered and hasn't lost since, now all the nuthuggers know his name.
Cro-cop vs. Wandy/Barnett- Cro-cop has been on a slump since then, but that night he was unstoppable and he let everyone he was for real.
Randy Couture vs. Father Time- His fight against Tito was supposed to be his swan song, and he was supposed to lose. Ever since then he's been defying the odds and proving people (and father time) wrong.
Bj Penn vs. Matt Hughes 1- Matt Hughes, riding a 14 fight win streak, came into the fight not only confident, but cocky as he said, "It would be embarrassing to lose to a lighter guy", "he can't even win at his own weight". Bj "embarrassed" Matt that night in his 170 lb debut.
There is so many, it really isn't fair to put into just 5 moments, but really only two of those moments belong on that list.