Gangrel: I'll still watch Gangrel moments and matches on YouTube to just see that entrance. Always liked it! Loved the ring of fire, the blood and everything was really well done in the entrance for the time. Just a shame he wasn't a solid wrestler.
The Undertaker (Ministry Years) and Ultimate Warrior are close seconds.
Old school Undertaker when it used to be all dark with a single strobe (no shitloadsa blue lights and thunder graphics)
Batista heel entrance with single strobe
Nexus because of their awesome theme
Kane's chemical entrance
The Rock attitude era
Evolution, best faction theme ever
On the flipside, I think Morrisons entrance is the worst ever, such a SHIT theme song :/