1. Octavarium - My #3 DT song, I haven't seen it live, it's a big fan favourite and it hasn't been played in ages
2. In the Name of God - Similar to the above, except its my #4 DT song. Probably not as big a favourite as 8VM, but I'm sure it would slay live and get great reactions
3. Endless Sacrifice - Another one of my favourites (just outside my top 10)that I've not seen live. I think it would work well live, with the trading solos and Train of Thought has been a little under-represented recently I think. However, this one has been played a lot more recently than the first 2.
Honourable mentions:
4. The Glass Prison - same sorts of reasons as the above - time it made a comeback!
5. Sacrificed Sons - I've always loved this song, especially the ending and I find it a bit underrated, I'd love to see it live. I also think this is probably a fairly comfortable song for James to sing night after night.
Just for fun, I'll add a few more I'd love to see: In the Presence of Enemies, The Ministry of Lost Souls, Lines in the Sand, Surrender to Reason.
The only problem is, my choices range from long to very long. If they happen to have an epic ~20 minute track on the new album, it's almost a certainty that they'd play it, meaning another epic (eg. 8VM) would be unlikely. That's why I relegated ITPOE down to honourable mentions.