In the last six months:
Black Country Communion (the celeb supergroup with Joe Bonamassa, Jason Bonham, Glenn Hughes and someone else). They've only played 2 concerts so far and I got to see their very first one in London).
Rodrigo y Gabriela (totally amazing and I have to see them again).
The Moody Blues.
Some that I remember before that, in no special order:
Neil Young (too many times to count)
Santana x 4
Ten Years After
Paul Rodgers x3
Page & Plant
Bruce Springsteen
Jean Michel Jarre
Pink Floyd
The Australian Pink Floyd
Think Floyd :)
Leonard Cohen x2
Peter Frampton
Richie Havens
Crosby, Stillls, and Nash
Alan Parsons (who so rarely tours)
Nils Lofgren
BB King
Jesse Cook
The Eagles
The Who
Paco Pena
Fleetwood Mac
Gary Moore
Deep Purple
The Counterfeit Stones (they were good!)
Jose Feliciano