Hm....explicitly purchased?
-A looooot of Dota 2 Hats/Compendium purchases
-Pretty much all ME1/2 DLC (skipped out on ME3's save for Citadel)
-Not sure if it counts, but a decent chunk of money on ME3 weapons, wised up after a bit tho.
-All of FO3/NV/Skyrim
-All of Fire Emblem Awakening (I'm weak, lol)
-All of the Halo 3/Reach Map Packs (except for the ones gifted, thanks Omlet if you're reading this! And Urk!).
-Borderlands 2 season pass.
-The XCOM DLC....Enemy Within made up for the smaller stuff.
-Wolfenstein: TOB
-Far Cry 3: Blood Dragon.
-Bioshock 2 Minerva's Den.
-Dark Souls 2 season pass
-League Skins from before Dota 2.
Most, if not everything else, has been part of a steam sale bundle.