RED stands for Retired and Extremely dangerous.
Loosely based on the comic book by Warren Ellis and Cully Hammer, it tells the story of Frank Moses (played by Bruce Willis) who plays a retired black-ops CIA agent. Assassins try to kill him and he ends up on a mission to find out who wants him dead and why. On this trip he ends up taking a customer service agent (played by Mary-Louise Parker) along for the ride.
This is an enjoyable romp full of explosions and ridiculous characters. John Malkovich playing the borderline insane Marvin Boggs is a particular highlight. As is seeing Helen Mirren wielding a machine gun.
This is a great cast (which also includes Morgan Freeman) and a great time.