6. The 2003 Chicago Cubs, National League Championship series
The choke: After fan Steve Bartman deflected a ball hit into the stands, arguably taking away an out from Cubs outfielder Moises Alou, shortstop Alex Gonzalez misplayed an inning-ending double play. The Marlins went on to score eight runs and then win the seventh and deciding game of the series.
Editor's Note: This entry originally stated the Cubs were up three games to zero. We've corrected the mistake and regret the error.