My copy of Crash Bandicoot 2 on the PS1. I lost it about 10 years ago, and have never found it to this day. I didn't remember lending it to anyone, so I think someone nicked it.

I've also lost my gameboy advance, which had my copy of Pokemon Ruby in it. That annoyed me, as I had a lot of good Pokemon on that! I really need to look through all my old crap thoroughly to find the bloody thing. I've also lost my pair of black shorts that I bought last year.

Its stupid really, as I take care of my important stuff. I have no idea whatsoever about what happened to my GBA.