rally towels on the court during a basketball game.
If you can't control your temper, don't go to sporting events.
I sat near or at the front of the ROC as a student for 4 years, never once threw anything. I have good seats now, been to a ton of games. Never once threw anything.
As a student, I laid into the refs too much occasionally, I know that. They're right in front of you and we screamed at them. But yeah, really mundane comparatively. The worst I said was "you suck" and "you're a cheater," but honestly: They were probably in the right. Mundane, and I was a 20-something college student.
Just saying: BYU fans, make sure you police those around you for major crap like this. Throwing stuff is never okay. Physically assaulting someone is never okay. Be welcoming to opposing fans, not confrontational (BYU fans are so ridiculously good at that, keep it up!).