I remember 'Step Up' being played in full back at a Projekt Revolution concert in Holmdel, NJ back sometime in August 2004 (they had us chanting "like this" during the chorus) just before they surprised us at the time with Jay-Z.
Anyways, I'd like to see any of these songs: High Voltage (remix), With You, Runaway, the Reanimation version of One Step Closer (with the current possible extended outro included?), Hit the Floor, No Roads Left, Qwerty, Blackbirds, Not Alone, Across the Line, Reading My Eyes, and maybe even do Crawl Back In from DBS.
Out of all those though, No Roads Left, Qwerty, Across the Line, and Blackbirds are on the top of my list.