Three different songs for three different reasons:
1. Pearl Jam - Alive. Mainly to watch their detractors' heads explode, and also so that once and for all people could hear them play a song by the band they've been accused of imitating and then say "shit, it's true they sound nothing alike."
2. Aerosmith - Dream On. They could really do a kick-ass version of this song. I can already imagine it in my head.
3. I would love to see STP cover something completely out of left field. Something you wouldn't expect Scott to sing, like a U2 song or something...