So far:
BRINK
The Darkness II
Garry's Mod
Hunted: The Demon Forge
Magicka
Trine 2
Two Worlds II
Terraria
Dead Space 2
I already owned SR3 (one of the best games I've played in years), Skyrim, Fallout:NV, and some of the smaller indie titles. I spent most of the weekend either finishing up games I already had or playing Terraria (11 hours this weekend alone).