The weirdest thing I've put in my washing machine is

[Fnaar]

Not washing machine, but the stories about mobiles reminded me...
Mrs F left hers on the beach (well, in the sand dunes behind the beach). It snowed the day after. She was convinced that's where it fell out of her pocket. We went back to the spot (snow had melted) and there it was. Working order too!

 

[4F]

Mobile in mine as well, did not work again.

However when I used to live at home my mum managed to put a chicken inside a tupperware in on a full cycle. She was defrosting it and to prevent the cats getting to it put it in a tupperware. Then she had the amazing idea of putting this in the washing machine incase the cats got the lid off the tupperware
(wtf ) and then forgot and added a load of washing in the machine and turned it on.

Quite how she did not spot the tupperware in the machine when she added the washing is anyones guess.