In 2001 we say a guy bring a can into the stadium, it was when they had boxes outside where you could drop off canned goods for the food bank. Anyhow someone brought in the can and launched it right into the BYU band and my understanding is that someone got cut open bad enough that it required medical attention.
I remember when I was a kid and my dad took me to the BYU/Utah game. The night before it had dumped a ton of snow. Anyhow BYU fans and the sidelines where getting pelted with snow balls almost the entire game. Ute fans have always been this way... It's their thing.