Gangster Squad (2013)

This is at heart a shoot them up movie with an all star cast.  So raised a bit above the fray by the talent there in, but contrained by the quality of the script.  It's late 1949, and as the holidays approach, former-boxer-turned-Chicago-mobster Micky Cohen (played in pretty unpleasant fashion by Sean Penn) has expanded Meyer Lansky's Jewish mafia to Los Angeles, where's he's planning to monopolize drugs and gambling and squeeze his bosses out of the equation. He means business, and is killing everything in his way to prove it.  The cops are largely on the take, as are the judges, but there is one, John O'Mara (played by Josh Brolin), who is not.  He tries to rally up a posse of cops to take him down before they have to strong a toe hold in the city.  Emma Stone is playing a dangerous game as Micky's bought and paid for girl but also the girlfriend of  Ryan Gosling, a cop with some ambiguity as to whether he is all in on the plan, at least at the beginning.  The good guys try to round up the bad guys and the shooting begins.