I've seen a fair few bands live, but the best would be Iron Maiden, Motorhead, Bad Religion, Nine Inch Nails and Marky Ramones Blitzkrieg for personal love of the music. For the actual spectacle of the performance, I'd say Alice Cooper and Rammstein. If you love a good mosh pit, though, nothing beats a Hatebreed, Skindred or Slayer gig. For laughs and audience interaction (and boobs), the kings are Steel Panther.
Actually, for a full list of what I've seen live (as some people are doing) look at my last.fm page [http://www.last.fm/user/Cpt_Oblivious]