Blood Simple (1985)

A bartender sleeps with his boss's wife and, because they apparently don't know how to work curtains, the private detective following them is able to deliver photos to the husband. There's a murder for hire, a cover-up, some double-crossing, and an amazing final scene that'll make you hold your breath. 

This is Joel Coen's first full-length directorial effort and Frances McDormand's first starring role and they really set the bar high for themselves with this tense noir. Its only real failure is in the casting of the extremely bland leading man.

A-