You can use an X-Box 360 guitar with this thing, too.

Frets on Fire is a fun game that can be used to test your musical skills and fast finger playing agility. The focus of the game is to a play guitar with your keyboard as accurately as you can. It works on the same basis as guitar hero, but ironically, you use your keyboard as your instrument. I highly recommend using the tutorial to get started. Remember it's all in good humor. This game can be run directly from a portable device and requires 52.1MB of free disk space.