Free Fire is the kind of film that'd materialise if you were asked to extend the final scene of Reservoir Dogs into a 90-minute film, and I've no complaints with that.
A Boston gun deal between some Irish and some international dealers go awry when two people on either side rekindle a private feud. A woman and physically large American arbitrating the deal are unable to prevent it becoming a mini-war. Throw in a double-cross and you've a film that continues to remain interesting despite the simple premise.
The film is funny, getting close to the level of the gunfights in Police Squad as the people throw things at each whenever the bullets ran dry. I also like that a lot of the quips the two sides throw at each other take place off-screen making great use of surround sound.