My favorite acoustic rock piece has got to be "Patience" by Guns N' Roses. The guitar parts are really different for a hard rock band, but it really showcases Slash's talent. Also, Slash did a song for a movie soundtrack. The song was called "Obsession"(be sure to listen to the solo guitar version), and it features beautiful classical guitar. Otherwise, I love "Tears In Heaven" by Clapton, and the already mentioned "Life By The Drop" by SRV.