I have a fair few! Mostly sex related.
Fairly inexperienced with 1st ever BF. He was a lot more experienced than me (and a bit of a dick). Was going down on him, when he, without warning (told you he was a dick), finished in my mouth. I only remember looking up at him completely startled, then throwing up all over him! Still makes me howl to this day. It all just came straight out all over him, the bedding, everything. I still can't even talk about semen in the mouth, or think about it without cackling like a witch.
Also farted in said BF's mouth once whilst warning him and trying so hard to wriggle away. He sulked so hard, refused to continue and left me lying in bed cackling away whilst he threw a tantrum that a 2yo would struggle to rival.
And my absolute favourite, which is not mine at all. So best friend had a love interest in uni, who had gone to the same high school as us. Said lad, had never had sex. He came across a girl on a night out, who lived in the same halls as him. They go back to his place and they have a bit of foreplay then dtd. After the act, he goes to his communal kitchen, to find himself covered, mouth and all, in blood, much to the horror of his flat mates. This is about 4am, and his parents are coming to pick him up at 8am to go home for Christmas. Poor lad, in his mangled state had to convince this girl to swap sheets with him. So his parents come to pick him up and he's got bloody bright pink unicorn bedding! Still makes me howl thinking about it. Poor lad.