John Mayer:
Neon, Gravity, Slow Dancing in a Burning Room, Somethings Missing, Why Georgia, Covered in Rain, 3x5, Love Song for No One.
Jack Johnsons:
Posters, Flake, Banana Pancakes, If I Could, "Sittin, Waitin, Wishin", Breakdown.... and a slew of others...
Shinedown:
.45, Beyond the Sun, Save Me (Acoustic version)
Metallica:
Fade to Black, Nothing Else Matters, Unforgiven, Low Mans Lyric.
Alice In Chains:
Anything from the Unplugged album... especially Nutshell
10 Years:
Wasteland... they don't really have any other acoustic versions of their songs..... I have heard an acoustic version for Through the Iris that was pretty sweet... I like their independant released album "killing all that holds you" too... check it out.
Eric Clapton;
Tears in Heaven, Wonderful tonight, Crossroads.... and just about any other song by Slowhand.
There's a pretty good list of songs to get you started....