Three guesses from the current hints :

- The Cat Lady
- Torchlight II
- Thirty Flights of Loving

Hints are : 88 metascore, 18+, no more than 1 year old game, never been bundled before.

Is Torchlight II 18+ game? I don't think so.

Neither is Thirty Flights of Loving...

Dunno, never heard about this game.

Look here - http://blendogames.com/thirtyflightsofloving/ - and be sad it is not this game. Then got buy it.

From Metacritic score of 88, released with the last year, I have found 4:
Far Cry 3 Rated M
Torchlight 2, Rating pending
Thirty Flights of Loving, Can't find a rating.
Diablo 3, Rated M.

I would assume that we can discount Diable 3.....

Yeah Groupees isn't always 100% direct with their hints, they've done the same thing in the past with their metascore hints (sometimes they're referring to reviews, and not the actual displayed score). I'm pretty sure it's The Cat Lady since the dev joined their chat and gave us some very direct hints.

I think it's silly to think it's anything other than TCL at this point, unless they add another mystery game.

One hint not mentioned here before - an adventure game ;)

What is so special about The Cat Lady, btw? Except for the fact it looks horrible? :P

I don't know about later on but the beginning is laughable. I imagine it gets better, though. Adventure Gamers really liked it.

The screenshots look pretty bad to me as well, but considering the glowing review scores I'm willing to give it a large benefit of the doubt :)

Don't forget with over 13180 sales we will have bonus game unlocked in +/- 24 hours @ the current rate.
So Airbuccaneers for everyone

In chat was mentioned word "flight" as clue. That could mean Thirty Flights of Loving as the mystery game...

It could also mean F(asterThan)Light, but I don't believe that myself ... ;)

It will take much more than 24 h to unlock bonus game, but I think it will be done before the mystery game is revealed. ;)