There's not much in their catalog that I haven't seen live, but here's a bunch that I haven't seen yet but would like to: Don't Look Past Me, The Way It Used to Be, Bombay Vindaloo, Barfbag, The Bigger Picture, Wither, Cry For Freedom, A Vision and March of the Tyrant.
I also would love to see any of the other songs in their catalog if they've redone them in a different style (like Surrounded '07 and Caught in Alice's Nine Inch Tool Garden) or added/changed parts of the songs significantly (like Metropolis part I '96 and Learning to Live '05), not to mention a new Instrumedley using instrumental excerpts completely different from the first one.