Here’s one for you, and you get to be amused at my expense! Today I made a rookie mistake…
It was my own fault, and I was in a bit of a hurry, not paying attention to my cable markings, and plugged both end of an ethernet cable into the same switch. For those not already wincing at that, this creates a broadcast storm. 
Luckily I knew right where the problem was when things rapidly started to go south. And I can take comfort in knowing that IT’s managed switches didn’t cap it either. Took down everything.
Yes, I fessed up to it. And also told them that i can take this facility down any time I wanted to-- and occasionally when I didn’t want to as well! 
Moral of the story: don’t do that. It’s painful. Not like sticking your face in a fan, but you know what I mean.