And now that day has come.
Senior design students at Texas A&M have designed a robot that can play the popular video game Guitar Hero (version 3, to be specific), by reading the pixel pattern on the screen as the notes stream and using actuators to hit the fret and strum buttons on the guitar controller appropriately. As a seasoned Guitar Hero myself I can see some room for improvement in efficiency (namely, it'd be great if it could hold down the fret buttons for repeated notes), but what can I say? I can't get 97% accuracy on expert on that song.
There's another video for a different song here.