John Francis Paciorek is an American former baseball player with three career Major League at-bats, all for the Houston Colt .45s in 1963. Paciorek is famous for having arguably the greatest one-game career in baseball history. After being called up when rosters expanded in September, he started in the final game of the 1963 season, on September 29, as the right fielder. Against the New York Mets, Paciorek went to the plate five times, hitting three singles and drawing two walks, for a perfect career batting average and on-base percentage of 1.000, scoring four runs and driving in three during the game. After appearing for the Colts against the Mets in a 1964 pre-season exhibition game, back injuries forced Paciorek to have surgery, causing him to miss the entire 1964 season. He then played in the minors until 1969, but never again played in the big leagues. Of the 20 players in major league history with career batting averages of 1.000, Paciorek was the only one to have as many as five plate appearances. Paciorek's brother Tom played for six major league teams during the 1970s and 1980s, and another brother, Jim, played 48 games for the 1987 Milwaukee Brewers. 

February 11th, 1945 in (Age 79)