Nothing terribly valuable, I'm only talking about maybe books or DVDs I have lent to friends and never seen again. I drop a hint-'did you enjoy the book/DVD?' and they reply 'Oh yes, I keep forgetting to give it back!' Then it gets forgotten again.
Of course I could just let it go, but it's annoying because I always return things quickly myself. It's bad manners though isn't it? I don't feel I can keep on asking for it back.
Lack of public toilets in towns.
Passports not in the drawer I always keep them in. Turning the place upside down.