well any metallica song, really
Dream on from Aerosmith would be great, you're right ... also Living on the edge.
I'd like to see their take on G'n'R - Welcome to the jungle
Normally, I'd reject any other voice than Layne Staley on Alice in Chains songs, but David would be the only exception. And since I know (because he said it a few times) that David loves AiC and their music is grunge with heavy metal influences, I would LOVE to hear Disturbed cover ANY AiC song, especially - Them Bones, Dirt, Man in the Box, Would...or Grind. My god, if they covered Grind i'd be the happiest person in the world.