Some of my favs to play/listen to acoustic:
A Perfect Circle - 3 Libras
Alice In Chains - Down In a Hole (Whole unplugged album for that matter... I had to buy the dvd cuz i loved it so much)
Collective Soul - The World I Know
Beatles - Blackbird/Mother Nature's Son/While My Guitar Gently Weeps
Pink Floyd - Wish You Were Here (Till Fred Durst Ruined It)
Radiohead - Karma Police
STP - Sour Girl
Filter - Take My Picture (Or whatever it's called)
Chevelle - The Red (don't know if theres a recording of it acoustic, but me and a couple peeps played it and it sounded real good)
and of course...
Toto - Africe (MUHAHAAHAA ITS FREAKIN TOTO!!!)
generally any Tenacious D song will bring out some laughs if u play it, I personally like the Ballad of Dio