I offered two, and then digressed into the story of a game that happened to turn down the same road.
Tonight, quelonzia and I stumbled across another iteration of the Yojimbo archetype: Fresh, with Samuel L. Jackson.
The story concerns a 12-year-old inner city boy who works as a runner for a couple of drug dealers. When the violence and degradation of their world comes home to him, he... all together now... pits them against each other so they take each other down.
It's an intense movie, especially since the 12-year-old actors involved are entirely convincing. Jackson plays only a small role, but, as the protagonist's chess-bum father, it's an important one.