IDK about best but New Age Outlaws with Road Dogg talking trash down the ramp was always one of my favourite.
The Rock circa 98 with a slower tempo and he had one circa 96-97 with "The Rock's layin the smack down".
Mankind's "Wreck"
NWO Wolfpac
Filthy Animals
Rey Mysterio's "What time is it"
Million Dollar Man, HaHaHaHaHaaaaaaaaaaaa
The hardcore Acolyte's theme, maybe it was the second or third they used.
Harlem Heat
DX theme, think it was called This Sucks and the X-Pac version with the rap
Eddie Guerrero had a few good ones, one of his earlier ones was that laid back funky beat with the La RRRRRRRRRRaza intro and his first Latino Heat theme was good and ofcourse his Lie, Cheat, Steal.
The best of all time imo was the Four Horsemen theme when that asshat Mongo McMichael was in it