Loonook, are you from the MTGNews boards?
Anyways, I vote Apocalypse. It's by far the most tweaked, freakish set WotC has ever made and has completely turned the game on its side, finally fully supporting every color combination. I don't know if it's really in theme with how the game was originally intended, but it's pretty freaking cool. My only beef with it would be the legion of chase rares. Almost all of the must-haves are rare.