'Midnight Cowboy' (1969)
Arriving at the end of a decade in which four Best Picture winners were full-throated Broadway adaptations, John Schlesinger's tale of a friendship between a con man and a gigolo woke up an industry that had been content to sing its way through the Vietnam War. The only X-rated film to ever snag an Oscar (even though the MPAA eventually forgave the "homosexual frame of reference" and downgraded it to an R), Midnight Cowboy was transgressive for its time, and its victory over Hello, Dolly! suggested the shape of things to come. Overnight, and for more than a decade to come, "nice" Best Picture winners became the exception instead of the rule.