Copious amounts of Trance and Dance music. Think of DJ Tiesto, Barthezzz, Score, etcetera. I mostly play trance while leveling because the music kind of keeps the adreneline flowing. Also works greately when I'm trying to learn myself how to code in C. But when I'm just playing around I more or less tend to use milder dance music like Gigi D'Agostino or CL&MT, which also works great with coding... Also, soundtracks of movies and games appear high on my list of favourites. (Like The Matrix, Gladiator, Braveheart, Final Fantasy VII/VIII and a few more) And lastly, when I'm in a more vile and evil mood I tend to play some Rammstein or Thyrfing.

Nothing beats L'Amour Toujours by Gigi D'Agostino though!