A classic spaghetti western and one of Sergio Leone's best.
This is the film that cemented Clint Eastwood into being remembered as one of genre's most remembered, although the concept in its entirety was stolen from Kurasawa's Yojimbo.
Its about a stranger who arrives at a remote Mexican Village, he goes to the local saloon where the innkeeper tells him about the 2 families vying to control the town as it's a hotbed for illegal gun sales between the Mexican and American army, the stranger see's an opportunity to use the families hate for each other and to makes some money by using his services as a gunslinger.
He takes advantage when a group of Mexican soldiers come through the village and are hijacked by one the village gangs and are killed, he uses this information to sell to the other gang, he then goes backwards and forwards between the gangs to use information against each other.
Along the way as he gets deeper involved he begins to see how innocent parties are affected by his involvement and the streets being a basic war zone and decides he needs to take a stand against both parties and do what is right.
A very good a film and a stone cold classic in the cowboy genre and if you haven't seen the film I am pretty sure most people know the classic ending.