"Sweet Child O' Mine" and "Killing in the Name" are good choices, with my only concern being whether they use the original versions or not, because I have my doubts about getting a good cover vocalist to mimic Axl or Zack, since a bad cover vocalist can really spoil a song (see "Ace of Spades")
"Freebird" - boo, I hate this song, largely due to it's ever-present spot on classic rock stations' daily playlists