I went through a bunch of my stuff yesterday and came across these codes I haven't, nor will ever use. Not sure what is or isn't valid anymore. They haven't been used, but may have expired.
Dead Space 2 Online Pass
Dead Space 3 Limited Edition Unlocks and Online Pass Code
Scribblenauts Unmasked Digital Comic
Darksiders II Cruicible Pass Code
South Park: The Stick of Truth Ultimate Fellowship Pack
Saints Row the Third
Online Pass - KAN7-5RN4-7JBB
Professor Genki's Hyper Ordinary Pack - D6FN-C6N6-KPTK
Mike Tyson Playable Character - K4KP=97NB-9NH2
Online Pass - 33AA-67ND-GPJJ
Good luck, and enjoy.