I'll second these two.
I'd also definitely go and see the Floyd show on July 6th, 1977 in Montreal. This was the show where Roger Waters spit on the fan, which inspired the concept for The Wall. I have the whole set, and it's really incredibly done; you can hear there's a lot of energy put into the music.
I'd also love to see a nuraber of others, like Jefferson Airplane, Zappa, SRV, Hendrix, Miles Davis (along with Bill Evans, Coltrane and the rest during Kind of Blue), Bob Marley, Cream, Pavarotti, Carlos Santana....In fact I'd definitely go to WooRABtock, I'd see Hendrix, Santana, Jefferson Airplane and a slew of others all at once. I'd probably venture back to Mozart's/Beethoven's/Chopin's time too, and listen to some of their works the first time they would ever be performed.