A few bluesy songs off the top of my head that can be done pretty well acoustic (it would help a lot if one of you could add in a little harmonica)...
City Boy - Keb Mo
Jumper Hangin' on the Line - RL Burnside
Ain't No Sunshine - Bill Withers
Night Train - Amos Lee
Wandering Blues - John Lee Hooker
Layla- Eric Clapton
A Change is Gonna Come - Sam Cooke
And this dude rocks the heck out of "Boom Boom" completely drunk, very likely insane, and all by himself on an acoustic, LOL.
"Boom Boom" John Lee Hooker by John Langford Acoustic .