This is tame in comparison to all your revelations but it really pissed me off at the time!
I always leave out shower gel, a towel and of course a bottle of handwash soap.
The guy in question went up to use the bathroom before the booking, he was nice and clean and the booking went fine.
It was only when I went upstairs after he'd left, to have a shower that I noticed to my disgust that he'd used my personal bar of Simple soap to wash his nob with. He hadn't just soaped up and used his hands tho'... Oh no... He'd obviously used the soap to scrub around his hairy balls, leaving my soap looking like it'd had a pubic hair transplant. Eugh!!
I hide my soap now... Dirty fucker!