I've volunteered for a few charity shops (UK version of a thrift store) in the past, the weirdest thing was the trash people would "donate", like used diapers.
In my 30's I worked with people with developmental disabilities. There was a 45 year old man I worked with occasionally who had brain damage from a fever when he was a baby. He had a strange fetish for dirty diapers and could not control it at all. If he smelled or saw a dirty diaper he was getting in there and there was no stopping it. I got called by his worker one day to help get him out of a dumpster. He found a bag of dirty diapers and was like a dog on a poop pile, rolling around and smearing it everywhere. Gross.