I've always really loved Edge's vocals on the U2 Go Home performance of Out Of Control. When he sings, "This one" at 1:28, it really resonates with me. http://www.youtube.com/watch?v=D0Ccp3xjc3Q
He also did harmonies to the Elevation version of The Fly during the chorus that I thought worked really well, but only in the early shows of the tour. Unfortunately, I haven't been able to find any youtube videos of it. I've just heard it on bootlegs.