From 1997: Cuba Gooding Jr.'s speech. The orchestra tried to play him off the stage, but it only ended making his speech sound all the more epic. By the end the crowd was roaring with approval and many gave him a standing ovation.
Even better, among those she beat was her ex-husband James Cameron, who actually took defeat very well, even joining in on the standing ovation she received.
From 2003: Adrien Brody not only winning Best Actor for The Pianist (becoming the youngest actor to do so, at age 29), but halting the playing of the wrap-up music, to the rapturous applause of the audience, and getting two standing ovations.
From 2014: Steve McQueen became the first black producer to win an Oscar for 12 Years a Slave which won for Best Picture. After giving his speech, he jumped with joy onstage while the cast and crew cheered.
Also, Lupita Nyong'o became one of the few actresses to win an Oscar for her film debut.
From that same year, Gravity completely destroying the Sci-Fi Ghetto, winning 7 Oscars out of its 10 nominations, including a well deserved Best Director win for Alfonso Cuarón (who also won for Best Film Editing earlier that night).