Here's my list:

copy verbatim the top section of kcarlile's post (starting with Metallica and ending with Days of the New)

Also, in no particular order:

Metallica (acoustic)
Bela Fleck and the Flecktones x2
David Brubeck
McCoy Tyner w/Stanley Clarke (WOW!)
Charlie Parker w/Norah Jones (WOW!)
Rush
Pearl Jam (acoustic)
R.E.M. (acoustic)
Ben Harper (acoustic)
Ben Harper and the Innocent Criminals x2
Dave Matthews Band (acoustic)
Blues Traveler (acoustic)
Smashing Pumpkins (acoustic)
Alanis Morissette (acoustic)
Neil Young (acoustic)
CSNY
Joe Satriani
Body Count
G. Love and Special Sauce
Josh Ritter
Paul Pena (amazing! mixes the Blues with Tuvan throat singing)

The ones I noted as acoustic were seen at a couple Bridge School Benefit concerts.