Mistake games

Payday 2. They keep making it worse and worse.

Please don't punch me, but WarZ

bought max payne 3 + dlc on sale.
23 bucks down the drain.

Assassin's Creed III. And I bought the special edition :'(

To be fair, from it I met a fellow hater who has since set me right with a copy of Witcher 2, so it's not all doom and gloom...

God Mode, Postal 3, and I kinda dissappointed in Saints Row 4, I should have just pirate it, complete and uninstall

Test Drive Unlimited 2

Quite a few actually.
NBA 2K13, even though is a really good game I grew tired of it.
Football manager 2013, forced myself to play about 10 hours or so, this made me realize I don't enjoy sports games anymore, not even sim ones.
Heart of Darkness DLC for Victoria 2, I preordered it, payed extra to support the company and the dlc broke my game.
TW Shogun 2, not as fun as I hoped it would be, I'm a huge TW fan since the original Rome, and I love the Sengoku Jidai period.
Civ V before Gods & Kings was released, now finally is a proper Civ Game.
Hearts of Iron III, just not fun, and overly messy/convulted, even for a grand strategy fan like myself (active in the Paradox forums).
Borderlands, just not fun to play SP, got a four pack and all my friends bailed on me...
Alan Wake + American Nightmare, the first wasn't bad, but it wasn't good either; American Nightmare is just plain silly and boring.

Bioshocks, Borderlands, Burnout Paradise, CS:GO, Garry's Mod, GTA IV, Hard Reset, Legend of Grimrock, and lot of others. All crappy games

bioshaku 2 because i paid 50 dollars for it

Homefront.

Possibly Dishonored.

Not quite what you're looking for, but I got Borderlands 2 as a gift for a close friend, and they haven't really played it (less than 7 hrs on record) :(

I regret buying the Grand Theft Auto Complete Pack when it was on sale.

Picking up GTA IV alone would have been enough (and half the price) to figure out I'm not interested in the series … Seems I enjoyed watching the Let's Play vids more than actually playing!

Homefront
Resident Evil
Modern Warfare 3

Transformers: War for Cybertron. For some reason the mechanics seem odd and I can NOT stay awake to even get past the first few scenarios. Also, Darksiders for PC. Constant freezes and I can't seem to find a good fix.

Ratchet & Clank : Full Frontal assault for the Vita.

Prison Architect

Spent $17 on it doesn't even work and I can't get my money back so yea huge mistake