Here is Rush’s La Villa Strangiato, considered one of the most technically challenging songs in rock music (by their own admission, they have a difficult time playing it correctly!):
http://www.youtube.com/watch?v=YQPHsONF_tE
Amazingly, for those that don’t the band, Rush is composed of just 3 guys: a bassist/keyboards/vocalist, a lead guitar, and a drummer.