OK great, I'll start.
Not me personally, but I once worked in a factory making car airbags and we suddenly became aware that there was a 'phantom shitter' on the loose amongst the workforce. Fresh poos would turn up in unexpected places e.g. next to one of the presses, under a lathe, and so on. This went on at least weekly for a while, until management gradually sussed who it was.... surreptitiously followed the suspect to the bogs, let him go into trap #1, then burst in, broke the cubible door down and caught him red-handed delicately placing a newly laid turd into a little plastic bag, ready to be deposited somewhere on the factory floor when he was unobserved. Turned out his brother had been sacked by the firm, he thought unfairly, and he was trying to get his revenge.