Not mine, but overheard. Age 15, camping at one of the big festivals, my tent backed onto the tent of a girl who was a mate of a mate. While sitting in my tent, it became clear that the girl in question was "entertaining" several people in her tent. There were three of us in my tent busting a gut trying to stay quiet, when she delivered the line, "Oh yeah, fuck me like your mamma."
Yeah, radio silence didn't hold after that.
And while living in houseshare, during a houseparty two of the guests got a bit randy in the bathroom (there was a muddy cockprint in the bath afterwards, don't ask, I have no idea.) There was a queue for the loo that all heard him going, through the door, "Ah, ah, ah, ah (beat) I'm sorry!" Oh, it loses so much not being able to hear the voice he said it in, a really high, childlike voice, like he'd just stood on her hamster or something.