Of all time, three stand out for me :
1) Bob Sapp v Great Muta (Tokyo Dome, 2004)
Bob's entrance, complete with dancing, feather boa and girls gyrating all around him to the tune of Madonna's "holiday" is one of the greatest and most hilarious entrances I have ever seen. Why on earth did Vinnie Mac not take a look at this and break the bank to sign him up, i'll never know. Who cares if he can't wrestle? Check it out on Youtube.
2) Chris Jericho v Gillberg (WCW Nitro, around 1997)
Hilarious parody of the Goldberg entrance, one of the funniest moments in wrestling. Getting lost backstage and the cheap pyro's were brilliantly written and one of the higher points in WCW history.
3) Ric Flair v Harley Race (NWA Starrcade, 1983)
The true arrival of Ric Flair on a global scale. The dark arena, the smoky atmosphere and the 2001 music blaring out. Although this was Flair's 2nd run as NWA champion, this was when he truly established himself as a world star.
Honorable mention to The Sandman in ECW also, great charisma and intensity and you can't go wrong with Metallica's Enter Sandman as a theme. Also, The Rock's recent comeback entrance will surely go down as one of the great ones (no pun intended).