Borderlands GOTY, Spec Ops, Left 4 Dead, DNF - pick 2 for Darksiders 2. I can add some indie game as sweetener.
I have Forge, Payday, 4 DOTA invites, and keys for Darksiders II, Darksiders, Metro 2033, Nexiuz, Red Faction Armageddon, Red Faction Guerilla, Saints Row 2, Saints Row 3, Supreme Commander, Supreme Commander: Forged Alliance, Titan Quest Gold, Warhammer Dawn of War II Gold, Warhammer Space Marine, Warhammer Dawn of War Gold, Warhammer Dawn of War II Retribution, Dues Ex: Human Revolution Augmented Edition, Hitman: Blood Money, Just Cause 2, Just Cause, and Supreme Commander 2. I also have a Wolrd of Warplanes beta key, 4 Crystal Dota2 Treasure Keys, and a Robot Chicken TF2 Hat. Can also make a small (<$15) steam purchase and gift it to you as well as everything above for your Arma 3.
As title says. Arma 3 = 19tf2 keys, Darksiders 2 = 6tf2 keys