Up to this point it's been Metallica (MoP and earlier works; without Burton they lost their edge) and Black Sabbath (Paranoid). Or a little talk radio if I'm not feeling like music. But recently on a whim I picked up a Johnny Cash CD.
I knew of him but not his music, but I have to say I've been listening every day for several weeks now. I'm pretty sure Folsom Prison Blues or A Boy Named Sue would get me going in the morning, and Flesh and Blood would set the mood for coming home from the woods to Mrs. Six.
Oh, and I can say there's nothing quite like flying down a deserted stretch of country highway before dawn with Ride of the Valkyries blasting!