AC from fatsand has the best soundtrack I've heard by a long shot.. any of the stuff on Skint Records just rocks. Rammstein/pennywise etc is cool for getting pumped up, playing loud and jumping around, but too much and it sounds like the same old ****e. It's a bit of a cliche that any 'extreme' sport shoud have a metal soundtrack.. a bit of variety's a good thing in my little opinion.
Anything on AC by Freq Nasty's my pick.
http://www.discogs.com/artist/Freq+NastyTrue story.. a few years ago I got my mate to crank this track
Sousound? (Freq Nasty Vs. Blim Remix)
www.discogs.com/release/160053on his fancy new car stereo -he worked for brisbane car sound at the time- half way thru this massive bass kicks in, then another layer even bigger & more distorted, by the end there was smoke pouring out of his new light-up crossover door panel and when we took it apart later there were bits fused together. After he got it replaced he never let me near his stereo again.

ps. I'll add a vote for the terorist too.