Pink Floyd
Roger Waters (twice)
David Gilmour
Grateful Dead (30+ times)
Jerry Garcia Band (12 times)
Allman Brothers (twice)
Robert Cray
Jimmy Cliff
B.B King (twice)
John Lee Hooker (3-4 times)
Santana (twice)
Hot Tuna (twice)
Jefferson Airplane
Bob Dylan
Paul Simon
Rush
Stevie Nicks
America
Three Dog Night
Gordon Lightfoot
Ottmar Liebert (a fantastic flamenco guitarist)
Jethro Tull
Heart
Metallica
Anthrax
Neville Brothers
Johnny Winter

With my parents when I was little
John Denver
Peter Paul and Mary
Arlo Guthrie
Joni Mitchell

Probably some others that I forgot