I work best in silence, but my family are noisy and annoying as fuck so I need something to drown that all out when they're home. White noise works well but I found that if I listened to it for long periods of time and then suddenly stopped my hearing went weird for the rest of the evening so I stopped that except for when I do past papers under exam conditions. Now I listen to "classical" (as most people would call it) or some ambient electronic music like Aphex Twin.
Dubstep/Hardstyle works well for when I'm doing maths homework because it gets me pumped up and I work through questions a lot faster.
If I'm doing research or something that's not really intellectually challenging like writing summaries I'll listen to whatever I'd normally be listening to.
EDIT: Forgot to mention drone metal, which I've recently started listening to. In particular,
this.