Get 'em while they're good - one use only, so if they don't work, you were too slow. All are for the PC versions as far as I know (They're from old Humble Bundles). You'll need to install Steam and set up an account, it you haven't already. Steam is great.
Saints Row : The Third - YZCY0-KVBQ6-CDK8P
Titan Quest (Without the expansion) - A2GQP-PHRHT-6JYJY
WH40K : Dawn of War (I think this is just the core game, without the Winter Assault expansion) - 2E4JQ-L2YWF-ZP0DQ
Introversion Bundle (Uplink, Darwinia, Multiwinia, Defcon. Did I mention Darwinia is the best RTS of the last decade? No? Well, it fucking is, and if you disagree with me, you are wrong. And a poor quality human being.) - 4HFZB-8RA3N-ZCG4K (Multiplayer keys are ASZORS-MGLVIA-CTVBFK-NNIJQI-INM and WRGKSO-XAWXRG-NCFOEI-YXRIRK-EMZ)
Gratuitous Space Battles / Cave Story+ - PCA0L-MMX2X-HYLG2 (Multiplayer HI4N-27AJ-UV3C-B)
Crayon Physics Deluxe - 7EJXP-P64A5-R4FDK
Eufloria - 3F0MJ-W2KKT-6W0QD
Superbrothers: Sword & Sworcery EP - DTLJ2-FM66Y-HK4A6
Machinarium - PX4W3-A7XKN-R3YMJ
Swords & Soldiers HD - 20YMH-FMYAQ-AP5FN
Cogs - VL67Y-NK8PA-I8BLM
Zen Bound 2 - NBZHW-4KAMK-5J6P2
Legend of Grimrock - PDN7D-JKVN3-B9JBF
Dungeon Defenders - E3X5A-ARXX4-XGGGF (Dungeon Defenders really pissed me off. It was a nice action-tower defence game, until the developers and their "community" turned it into a shitty MMO.)
Bonus! Desura key for the Introversion bundle - INTRO-Y41OP-BGM0G-N5PUY-7JGLS - and Dungeons of Dredmor - NLF23-NT72Z-JIOK0-WQUC9-2J8KZ.
Thank you, and Merry Christmas from Something Awful! These codes have gone to loving goons who surely appreciate your generosity. :)