What's the weirdest thing you've found behind a server rack?

I'm doing a deep-clean of a cage that's been running untouched since 2019 and so far I've unearthed a crumbling protein bar, a mouse nest made entirely of cable ties, and one unlabeled USB stick that I'm too scared to plug in. Curious what other people have found living in the forgotten corners of their work lives. No judgment, just want to know I'm not the only one who keeps a 'do not touch' pile.