While in SF recently, I stayed with friends who had just moved up there, and they turned me on to a Playstation game called 'Guitar Hero'.
If you've ever caught yourself playing a bit of air guitar, you would have fun with this game. The game controller is a plastic guitar shaped controller which you hang from your neck by its strap. You have 5 'fret' keys by your left hand (assuming you are right handed), and 1 'strum' key for your right hand. The game has some great songs; while a song plays, your job is to watch the 'notes' come toward you, and, in rhythm, strum the guitar while holding down the correct combination of fret keys.
It's not as complicated as a real guitar, of course. But it's fun, and you get the same fun feeling that causes people everywhere to play the occasional air guitar. And there's more than I've gone into here: the guitar does have a whammy bar, and you can rock out extra hard by tilting the guitar up vertically.
It's silly fun, but isn't that all you can really ask for?
Link: 'Guitar Hero' on metacritic.com (where it has a 92 out of 100)