Led Zeppelin. I had tickets for the Presence tour, at Madison Square Garden, as a senior in high school but caught the measles. I did get out of a calculus final, though.
The Band, with Robbie Robertson. I could've done this on their last tour as we were allowed to go to concerts with friends at age 16. Saw the ad, thought about it.
Pink Floyd, with Roger Waters. I tried to get tickets to The Wall and Animals tours, but was shut out. They had a mail order system.
(Also, the Clash with Mick Jones. I saw them post-Mick but they were a shell of former selves by then.)