In mostly order from most fav to less for playing disc..... Bob Marley, Pink Floyd, Sublime, JJ Grey & Mofro, Primus, The Doors, Tool (though I love Tool, seen them twice in concert, just like mellow music when playing), Dresden Dolls, Cake.....
I was on the fritz about whether my Ipod helps or hurts my game for awhile; I decided it's a scenario issue. If I go play a round by myself, I jam out the whole time and I play just fine, if not better than usual. When I'm playing with other people, I find it's distracting: play, pause, play, pause, "huh, sorry had my Ipod on", trying to find the right song and so on. It takes away from the good times I should be having with my friends.
In a tournament, I keep the Ipod in my bag just in case I end up with some irritating person on my card and need to tune them out. My goal is to remain focused and relaxed. I'm not sure music helps with either. I guess it depends on my mood: do I want to talk and have fun or be serious and play my best (hopefully).
When I do jam out during a round, my favorite is Snake River Conspiracy. Hard-core chics ROCK! If you've never heard them, I have some on my page.