I dont listen to anything, I'm too concentrated on torturing myself as much as possible to care about what I listen to. They play the same old stuff at my gym anyway, I dont hear it anymore.
On the way to the gym I do crank up some hard house tho, sometimes some grunge/metal aswell.
I like to feel pissed off when I get in the gym, so if someones done something that really irritated me in the day, I focus more on that than music; and use them as a point for power!!!
Grrrrr