Tie -

Either all of Montery Pop - Especially Janis, Otis Redding, Who and Hendrix America Homecoming

or

Velvet Underground during their Exploding Plastic Inevitable days.

I don't have any specific shows. Monterey Pop Fest would've been cool. Seeing This Heat play while they were working on Deceit material would be incredible.

Being in New York in '78 would be insane.

I can answer this question by thinking back to a band I could have seen live, but when I just wasn't quite sophisticated enough to know better! That band is Neutral Milk Hotel. I wish I would have seen them before they dissolved because I can't imagine what his voice sounds like live.

I'm paying attention now.

Nirvana, Queen, Pink Floyd are up there. Although I'd really like to have seen an early Joy Divison show. It seems like the atmosphere would be kinda trippy and fun.

When Dylan went electric... partly to see something historic... partly to see the fans mad

or to see Radiohead again

Beatles rooftop performance
Bob Dylan when he went electric
Pearl Jam when they were just starting

Grateful Dead, preferably a show from their Europe Tour. My uncle was a roadie for that tour, and I'm infinitely jealous of him.

To be honest, I can't really say what I'd love to see. Would take some thinking.

However, one concert that immediately pops to mind, is Judy Garland, April 23, 1961, Carnegie Hall.