Keys.

I'm assuming they open doors to various places I've lived or worked. Most of them look the exact same and I can't, for the life of me, figure out where they belong, so I'm throwing them away.

Note to Reader: If I am a friend of yours, and you gave me a key to your place to hold onto, I'll need a new copy. I'll also need you to be ok with me throwing your key away in a year. Thank you.