Well, there are a lot of things I would like to hear. P5hng.Me.A*wy, the reanimated bridge of OSC, the Numb's intro from 2004, etc...
But most of all, I would die to hear an acoustic live! When I say 'accoustic', I mean it, not only 3 songs, like "KROQ Almost Accoustic X-mas" 2001. Would be amazing!