Welcome! Here are some tips for using this forum.
Strangest thing that you have found in a unit
Today I was sent on a maintenance call for a new customer with an oil fired boiler. I arrived to find a fairly new Weil McLain P-WGO-3. It was installed without a low water cutoff and a few years ago someone put anti-freeze in the boiler but didn't bother to install a backflow preventer. But the oddity that I discovered was inside boiler on top of the sections.
Looks like Tweety Bird got a little too comfy on top of the chimney.
I've found plenty of mice nesting inside of A/C condensers, bats in attics, pornography stashed away by the system, drug paraphernalia and I'm sure a few more will come to me that I've tried to forget, but what strange/wierd things have you ran into while out in the field?