In no particular order:
The Beatles - specifically the Rooftop performance in '69
Allman Brothers - any show with Duane, and narrowing it down a bit, mid to late '71 when they started adding "Blue Sky" to their setlist
Derek & the Dominos - any show that Duane played in
Little Feat - only saw them once and would love to see any show with Lowell again, the '75 and '76 tours were pretty good, maybe one of those shows
SRV - another artist that I only got to see once. Any performance from "The Fire Meets the Tour" in '89 with Jeff Beck woulda been an awesome one to see.
Jimi Hendrix - any one of the Berkeley shows in '70
Weather Report - Heavy Weather tour - ironically, on the night I saw Little Feat in '78, Weather Report was playing at a different venue. After his show, Jaco showed up and sat in on "Teenage Nervous Breakdown."
Stones - '71 or '72 tour - imo, musically, the group was at their peak
Roy Buchanan - any show
Neil Young - Rust Never Sleeps tour
Santana - Abraxas tour