Hrm. *scratches head* Well, it can't be Beautiful Day, Elevation, or Until the end of the world, because he's not wearing glasses, and his mike is on a stand. It can't be Kite, One, or Walk on, because he doesn't have a guitar. The lighting is very bright, so it could be Streets or Pride. I don't think it was Out of Control, because I only saw them do that at LA3, and I saw Bono do this at least twice. New Year's Day wasn't performed at LA3, but that's a good guess. In a Little While is a good candidate, but they didn't do that song at any of the three 3rd leg shows I saw.
The word "heart" appears in the following songs performed at the three Elevation 3rd leg tour shows I saw. (Sorry I didn't do this investigative work first--I thought sure someone would know).
Wild Horses (LA3)
Beautiful Day (all)
Walk On (all)
Bad (hm, is this it?) (Vegas/LA3)
Sunday Bloody Sunday (all)
So after looking into this further, my guess is Bad. Any other guesses, or did I officially just kill this thread?
--
Well you left my heart
Empty as a vacant lot
For any spirit to haunt