I don't wanna include pride ko's to me they will always be separate
These are my personal faves
Anderson vs Weidman
Page vs Liddell
Rashad vs Liddell
Ace vs quarry
Anderson vs Ace I
Leben vs martin
Lil evil vs john Lewis
GG vs CC
Anderson vs vitor
Wand vs Stann
Add rampage vs wandy (in the UFC) to the list
EDIT: Also add this one to the list...
Just look at Tank Abbott's fights, that's the top kos.
No love for Kimbo knocking out Tank with air from an uppercut?
I think one of my favorites is Jeremy Stephens uppercut from hell against Dos Anjos.
Also and though this is not Zuffa Patrick Cote against Bill Mahood.