If you want a band that does superb covers, Dream Theater is the band, they have done a ton, and too much to name so you can see all the covers they've done here.
http://en.wikipedia.org/wiki/List_of_songs...y_Dream_Theater
Noteables though are Iron Maidens- The Number Of The Beast, the entire album, Metallica-Master Of Puppets, the entire album and Pink Floyd's- Dark Side of the Moon, the entire album.