In the Heat of the Night (1967)
What is it? A Philadephia homicide detective (Sidney Poitier), despite initially being treated as a suspect, offers to help the racist Sheriff (Rod Steiger) of a small southern town investigate the murder of a rich white man.
Why did it win? There's been a whole book written about this Oscar race (by Mark Harris; Pictures of a Revolution) but to sum it up in a few words (or try to): in the middle of the Civil Rights struggle, Hollywood was trying to be radical without actually being radical. Hence this muted plea for racial tolerance was more palatable than the edgy sexiness of Bonnie and Clyde or The Graduate, more effective than Guess Who's Coming To Dinner and better than the overblown mess of Doctor Doolittle.
Did it deserve to win? In terms of enduring popularity, fellow nominee The Graduate is probably the deserving winner; in terms of daring at the time, it might be Bonnie and Clyde; not even nominated were The Jungle Book, The Dirty Dozen and - most egregiously overlooked of all - Cool Hand Luke. Oscar, the dude ate fifty hardboiled eggs: what does a guy have to do to impress you people?
Worth a look? Maybe, for Poitier's smouldering rage and iconic "They call me MISTER Tibbs" line.