Look, I could write something hilariously witty that would cause you to lose your job, because you laughed so loud. But why waste your time and get you fired, let's get to the Mascot Off!!!!
Let's start with the classic, of course. Oski v. The Tree (and an updated version):
This one is fictional, but we had to put it in.
And again, but this time, sped up!
Go Cougar (Note: Houston, not Wazzu):
What are these? They totally lack context. And some have loud sounds so watch your volume:
Damn, Steve ColbEagle got dominated!
That's some goooooooooooooooooooooooooooood fighting! GO BEARS!