I like heavy metal music that fits with what I'm going for, especially for tough battles. For instance, I played Immolation's Swarm of Terror when the group had to tackle a Monster of Legend Hellwasp swarm.
Other than that, I reccomend classic older rock in the background because its usually pretty high quality and liked by the most people. Its rare when somebody will bust your balls for spinning Clapton, Rush, Queen, Rolling Stones, Led Zep, etc. For me I don't like the music to be a big part of the campaign unless used to make a fight against an important critter memorable. If i may be so bold to reccomend rap like:
Gangsta rap
Anything with Viktor Vaughn in it
Any rap that is a little older, out of the mainstream, or upheld as quality.
A lot of people say they "hate" rap. I don't think they've ever head rap. I like to listen to goofier bands like the Beastie Boys and Dangerdoom and MC Chris for the goofier campaigns like Hackmaster.