Whenever I go to a baseball game with friends, we think about what we would want played if we were coming up to the plate. The most consistent answer I've ever had was "Rock the Bells" by LL Cool J, starting with "I excel, they all fail..."
But! What if I was a fighter? In that case, I think I'd want to go a little less retro and a little scarier. I was thinking M.I.A. or "Sabotage" by the Beastie Boys (if I was more religious, maybe "God'll Cut You Down" by Johnny Cash) but then...I think "You Don't Like It" by Jean Grae would be more intimidating:
Runner up: "Fruit Juice" by Snoop Dogg...I mean Snoop Lion...because I love the weird reggae vibe mixed with heavy beats. Somehow I think that might be terrifying.
The best example of bull rider entrance music I've EVER heard was "Semi-Charmed Life," but just for fun, mine would be the chorus (you only get like 20-30 seconds of music) of "Gunpowder and Lead" by Miranda Lambert:
How about you guys? Ever consider what music you'd want to use to intimidate the pants off people? What sports? Or do you imagine entrance music in everyday situations? I often wish I had it upon entering meetings.