Payday: The Heist has a brilliant concept, but a flawed execution. It mashed L4D's gameplay with the theme of famous movie heists, except that it didn't quite get what's superb about either. While each heist starts off as being exciting and cool, by the time you killed off over 100 cops in less than 15mins the rush and fun factor is gone and it's more about finishing the mission ASAP than enjoying it.
Pros: A blast to play with friends, when everyone knows what they're doing it's a great challenge on higher difficulty, variety of maps, some maps are excellent, good gunplay, friendly AI is decent
Cons: Overly high accuracy of the cops (especially through smoke), neverending waves of cops and extremely limited ammo, doesn't work all that well in the more open areas because of the mentioned problems, problematic support for the microphone, most of the maps are small with limited replayability, limited arsenal of weapons and equipment (especially in the beginning), forgettable characters

A refreshingly different first-person shooter.

Variety! Great!
Co-op! Sweet!
High difficulty! I love it!

In Payday you pull off a series of heists to earn some big cash. No war, no military, no aliens – just simple and clean cop-killing. The game is designed around the idea of 4 players playing co-operatively, with buddy AI helping out if you're fewer. The heists feel unique, almost each one is an homage to a great heist film. You level up automatically by playing the game, but you can choose for which leveling tree the level-up counts: Assault, Sharpshooter or Support.

Granted, the game's not very strategic – you kill a lot, press [F] a lot. But it's fun, nevertheless. Especially with friends.

Free to own on Steam for the next 24 hours

http://store.steampowered.com/app/24240/