was a huge hit for the PlayStation 2 console. Using a special guitar shaped controller you could "play" a variety of rock hits, hitting the fret buttons in time to on-screen cues. Well now there's an Open Source cross platform clone of Guitar Hero called Frets on Fire
which includes support for OS X. The program was originally designed to be played with a keyboard, but at least with the Windows version, you can use the actual Guitar Hero controller (along with a PlayStation 2 to USB adapter) to play Frets on Fire on the computer. Unfortunately, I haven't been able to determine if the controller also works with the Mac. So anybody out there "jamming" on the Mac with the Guitar controller?
[Edit: those of you having trouble on PPC check out this forum thread