BattleBlock Theater, Bastion, Call Juarez: Bound in Blood, Call of Juarez: The Cartel, Call of Juarez: Gunslinger, Castle Crashers, Far Cry 3 Blood Dragon, Return to Castle Wolfenstein, S.T.A.L.K.E.R. series, Serious Sam complete collection, Vampire: The Masquerade - Bloodlines, and Wolfenstein: The Old Blood. Thinking of grabbing Saints Row: Gat Out of Hell before it all ends. I was certain I picked up Bully: Scholarship Edition, but it looks like it's not in my library. Oh well.
Already cleaned of Wolfenstein: The Old Blood due to it being a super solid but short FPS, Serious Sam 3 BFE trips up my failing PSU and is thus unplayable, Call of Juarez: Gunslinger and Call of Juarez: Bound in Blood I've already completed previously and know they're both really fun games (Gunslinger being far better in my opinion), S.T.A.L.K.E.R. is mean and everything is painful and I love it already.
Some games I hope to get to at a later date, namely Bastion and Vampire: The Masquerade. A lot of games I got simply because they were stupid-cheap, even though I have little intention to play them (BattleBlock Theater despite its huge critical acclaim, Castle Crashers, Far Cry 3 Blood Dragon).
Some games I regret leaving behind, like The Witcher series, Transistor, Life is Strange, Telltale games, Far Cry 4, GTA V, and Watchdogs. But the price was a little too high, or I wasn't realistically going to play those games anyway. This year's sales were so-so, since the sales people cared about weren't that strong (ARK, Dark Souls), or straight up were the same as the retail price but marked up in anticipation of the sale (GTA V).
Shoutout to the Call of Duty franchise, by the way. Call of Duty 2, which came out in 2006, almost ten years ago, went on sale for $10. Black Ops 1, almost five years old now, is on sale for $40.