I'm surprised no one has mentioned Exit yet...you kinda HAVE to crank that song up to even hear it!
but once you do, and once it really kicks in... brilliant. What a fantastic song.
Vertigo of course - seriously, everytime Bono says "turn it up there, captain" I do. Elevation (especially the Tomb Raider mix, or live), The Fly, Love and Peace Or Else, Discotheque, Do You Feel Loved (that BASS!), Gone, Miami (yes. I like Miami. in fact, I LOVE Miami.), Streets, Until the End of the World, Beautiful Day (live especially), New York, I Will Follow (or hell, the whole Boy album), 11 O'Clock Tick Tock, Zooropa (it's kinda quiet at first and you wanna get the full effect when it kicks in), Sometimes... (again, quiet and the kick-in...sometimes emotional songs are meant to be cranked too), Dirty Day, Sunday Bloody Sunday (especially live, like from UABRS... gotta crank up that perfection), Like a Song...
hell, let's just crank up all of 'em, they're all worthy