Recently got an album at our local art fair of an artist (can't remember the name exactly) who plays the chapman stick. It's basically a guitar that you tap to make the sounds, so it plays like a piano but sounds like a guitar. You can play the melody and background with both hands. The artist is doing some Beatles covers, it's pretty cool!
EDIT: Bought a Vince Guaraldi greatest hits CD at a GoodWill for $1. He's one of my favorite artists, known mostly for the music during the Charlie Brown specials, but also does some amazing jazz, latin and general "coffee house" sounding music.