Got a couple...
1) Went to a party one night many years ago as a teenager, kid hosting was an asshole prep and I didn't want to go but a few of my friends drug me along. Long story kinda short, a couple of jock asshats (host included) kicked the shit out of this one kid after about 20 minutes of verbal abuse, all because the kid was a little loud and drunk. During the verbal barrage they were giving this kid, they started calling him a faggot and all kinds of other stupid shit that was just bang out of order, so my friends and I decided to go upstairs and piss on all the bed pillows. One of my friends apparently decided after that, that it wasn't enough. He goes into the bathroom, drops the nastiest shit IN the sink, then puts all the toothbrushes in it, lightly rinses them off and puts them back in the mirror cupboard. Word got out a few weeks later about what happened, not who the culprits were thankfully, and even after a big shit was left in the upstairs sink, the kid never knew about the toothbrushes and continued using his, as well as his sister. That was damn near 15 years ago and he still deservedly gets stick to this day.
2) A few years ago while working as a manager with Wal Mart back in the States, some older guy in his 60s or 70s comes in with a few empty buckets of ice cream. All clean as you like. Well, he wanted his money back, saying how they went out of date. After facepalming, I rejected the refund and he really laid into me for a solid 10 minutes. Honestly thought the guy was going to have a heart attack he was turning so red in the face. Guy all of a sudden says "FUCK THIS..." and walks away, not toward the exit but toward the back of the store and the rear bathrooms. I of course follow at a distance just to make sure he doesn't cause trouble, he goes into the loo and is in there for a good few minutes before people start coming out laughing. A couple of people go in, then immediately come out so I'm thinking "oh fuck, what's he doing..."
I walk in and this 60-70 year old man has dropped his trousers to his ankles, backed his ass up to a urinal and is trying his damndest to have a shit in the urinal. We just kind of look at each other for a second before he says "YOU ENJOYING THE SHOW YOU FUCKING QUEER??" in the best old guy voice ever. I call another male manager to come over from my radio, flip out the phone and call one of the cops I have on speed dial, the aurl fella figures out I'm on with the cops and comes at me with his pants down. Fuck sake, we had to restrain this guy with his pants around his ankles, shit all over himself, face down in a Wal Mart bathroom. Probably the funniest thing I've seen as a manager.
3) Pretty tame compared to some here, but another Wal Mart story, was on the front end near the checkouts when coming from near the entrances, this woman screaming angrily at this skinny teenage kid wearing a sleeveless shirt, baggy tracksuit bottoms and flip flops. The kid is just calmly walking toward me and toward the front bathrooms. My loss prevention manager comes running through the entrance yelling "GRAB HIM, GRAB HIM!!". I was a bit bigger than him so I step in front of him and he stops, calm as you like, just looks at me and says "What's the problem?". Loss prevention guy swoops like David Hasselhoff out of fucking nowhere and tackles the kid.
After the cops get there, the kid starts crying and it all goes down. The cop that shows up just happens to have been his arresting officer on a previous occasion when he and his brother commited armed robbery. Apparently the kid was riding with his step father when they saw a woman driving down the road with her pocket book on the back of her vehicle. They followed and waited for it to fall off before they got it, emptied it and drove off, eventually realizing she had double backed and was now chasing them. Anyway, the cop gets the kid stood up and asks what the bulge in his pants is, to which he says "it's my cock", cop takes him to the bathroom to search him then I hear a ton of laughing. Kid had about a pound of reefer in his trousers. The lady who he stole from was chasing them and flipping out on him so much he knew the cops were going to eventually get involved so he was trying to flush it.
Deep inside I've always hoped he got the pot from that ladies purse.