On July 24, 1983, with two outs in the top of the ninth inning, George Brett of the Kansas City Royals hit a home run against the New York Yankees. With a man on base, it moved the score from 4-3 Yankees to 5-4 Royals.
But it actually turned into what one wag called baseball's only "game-losing home run," when Billy Martin, manager of the Yankees, pointed out to the umpire that Brett's grip-enhancing pine tar had been applied illegally far above the end of the bat. The umpire ruled, correctly, that that discovery nullified the home run.