Since I've only had this laptop for three months and since I usually tend to listen to my music library on shuffle, these results are somewhat inaccurate.
1. Echo & The Bunnymen - Going Up (16 times)
2. U2 - Dancing Barefoot (16 times)
3. Echo & The Bunnymen - Rescue (14 times)
4. U2 - Miami (12 times)
5. U2 - Mofo (11 times)
It's probably more accurate to look at my Last.fm top tracks, as I started tabulating those when I was still on my old kaput desktop.
1. U2 - Zoo Station (81 times)
2. U2 - Bullet The Blue Sky (74 times)
3. U2 - Where The Streets Have No Name (73 times)
4. U2 - Even Better Than The Real Thing (64 times)
5. U2 - Miami (57 times)
Even those are slightly skewed, as Last.fm can't distinguish between live tracks and studio tracks. Bullet and Streets wouldn't be nearly as high if it weren't for the fact that they're on practically every bootleg since 1987.