I'm fairly sure that everybody, if not most of us listen to music while playing Guild Wars. So why not share what we listen to, and we could even learn from each other!
What I listen to depends on what I am doing. When roaming and being a ninja in WvW, I listen to Dan Bull's Thief rap. When in a zerg, I usually listen to two steps from hell.
When dungeoning, I listen to Two Steps from Hell, the Crysis 2 epilogue theme or Kokuten from Naruto. When on a boss, however, I listen to the guitar version of Emiya, or if I'm listening to Kokuten, I keep listening to it.
When doing world completion, I listen to GW2's amazing soundtrack, usually the Sylvari theme and the Tengu Wall
So, what do you listen to when playing guild wars?