A few of my pet peeves include:

Cheerleaders doing stunts (or worse, starting chants) during an athlete's routine. No one cares about your heel stretch just right now, folks. 

Teams doing the 10 hands. I don't know why, but it's always rubbed me the wrong way. 

Hearing any of the following songs in the arena: Let It Go, Can't Hold Us, Chicken Fried, or Sorry.