What's the dumbest thing you've seen other players do?

Just today, I was ubering a soldier, and there was a lonely lvl 3 sentry just around the corner when you come out of the left tunnel on the first dustbowl stage. Then about 3 seconds in, he randomly switches to his equalizer to beat the shit out of the sentry. I hated that weapon a lot already, but now.... I was totally speechless.