I have the PS3 version of COD Ghosts which came with the PS4 upgrade key which allows you to upgrade to the PS4 version for $10. There's a catch: you must have the PS3 disc inserted in the PS4 in order to play, therefore you must have a PS3 Ghosts disc. The key expires March 31st and I won't be getting a PS4 until later this year, so maybe somebody out there has use for it. I'm not sure if they region lock these keys, so it may only work for North America; I have no idea if they actually do this though.
More info: PS3 to PS4 Digital Upgrade Program
First person to give me a valid reason for wanting it gets it for free, via PM. Also, the person must have over 100 posts here on Neowin.