Ben Heppner at the Chan Centre for the Performing Arts. I've never been interested in any other kind of concert.
Niccolò Paganini. What I wouldn't give to see his left-hand pizzicato and ricochet staccato. I could just get "Itzhak Perlman: Live In Concert" on DVD and it might even be better with 200 years in between, but since time is not a concern, I'd like to see it from The Original Master. And I'd like to see just how insane he really was. =)
I would have liked to see Victor Borge live. There's so much musical and comedic talent in that man that he needed a seatbelt. =D I would have loved to attend his "Happy Birthday" show where he parodied Classical composers in the way they would have written the "Happy Birthday" tune. It's absolutely brilliant to hear it on MP3 now, it would have been even better to see it live.
Jerry Goldsmith is the other composer I'd like to meet. He's still alive, he did the music for most of the Star Trek series and movies as well as many others with tremendous soundtracks: First Knight, The Mummy, Mulan, Air Force One. I guess Howard Shore is good too, but I'll forever wonder how great LOTR would have been if Jerry Goldsmith did the musical score.