Now that Guitar Hero III is out - and my friend got it even before it was officially released, somehow - we've been playing that (and the obligatory Halo 3).
Guitar Hero II was the first one that I played and bought. For those who don't know it, it's a musical rhythm game that has you "playing" a toy guitar to match the music / frets going by on the screen. It's an awesome party game, and the soundtrack and art are great.
It also introduced me to / reminded me of some bands and genres that I hadn't listened to in a while. Classic American and British Rock and Metal are up there as some of my favorite kinds of music to listen to these days. In this mixtape, you'll find: