I'm partially biased becuase it's one of only a handful of fights that I have seen live but Hunt vs Bigfoot gets my vote.
Frye vs that one guy at Pride. I think it was 20 or 21. They just grabbed each others head and started swinging
rickson vs funaki
so many great fights its hard to pick one
Hendo/Shogun 1
Fedor/Crocop
Hughes/Trigg 2
Hunt/Bigfoot
Nog/Sapp
Frye/Akiyama
Jones/Gus
idk probly many more but i cant just pick one