Rammstein, Rage against, Slipknot, Korn, Prodigy, Static-x and other similar angry music, if its a heavy set day, such as squats or deadlifts etc.
If its a cardio day then, its an Armin Van Buuren trance mix, he has over 400 public radio broadcast mixes, and most of them are amazing.
I think the heavy music really helps get me in the mood for lifting heavy, adrenaline boost etc
When I get home I'll post up my play list for you to have a gander, maybe give you some ideas!