Key from here for Duke3D if its steam game:
Brazen Prototype
Demigod
EETS
Hoard
Critical Mass
Zombie Shooter 1
nMomentum
Hacker Evolution: Duality
Your Doodles Are Bugged!
Zombie Shooter 2
Hacker Evolution: Untold
Hacker Evolution
Serious Sam Double D
Serious Sam: The Random Encounter
World Of Goo
Rochard
Flatout
Faerie Solitaire
A.R.E.S.: Extinction Agenda
Osmos
Zero Gear
Revelations 2012
Metal Drift
Xotic
Xotic DLCs
Sideway New York
The Ball
Nikopol: Secrets of the Immortals
Cubemen
Worms Blast!
The Ship Complete
Avernum: The Great Trials Trilogy
Eufloria
Crayon Physics Deluxe
Metro 2033
Awesomenauts Yogscast Skin
Spacechem
DOTA 2
Cogs
Swords & Soldiers HD
Avadon: The Black Fortress
Magicka
Home
Victoria II
Superbrothers: Sword & Sworcery EP
Sanctum
Titan Quest
Warhammer 40,000: Dawn of War
Galactic Arms Race
Twin Sector
Lume
Loadout Beta
Solar 2
Shank 2
The Binding of Isaac + Wrath of the Lamb DLC
Cave Story+

1 tf2 key for your dota 2 inventory ?