In the history of major league baseball, has a dropped third strike ever impacted a playoff or World Series?

1941 World Series - Game 4

Thanks to Pete Reiser's two-run homer and pinch-hitter Jimmy Wasdell's two-run double, the Dodgers clung to a 4-3 lead after eight innings. After relief pitcher Hugh Casey retired the first two Yankees in the ninth, the Dodgers were just one out away from evening the Series at two games apiece. Casey then struck out Tommy Henrich ... but the ball got by catcher Mickey Owen (who was charged with a passed ball), and Henrich scampered to first base. That opened the floodgates, as Charlie Keller and Joe Gordon eventually rapped two-run doubles, propelling the Yankees to an improbable 7-4 victory.

As an aside, Bob Elson was the radio announcer, and when Henrich swung and missed, he prematurely said that the Dodgers had won. The Brooklynites claimed that he had jinxed the Dodgers, and Elson never went back to Brooklyn.

Casey's pitch was a spitball that jumped two feet. Henrich had no chance to hit it and Owen had no chance to catch or even block it. That's apparent even on the grainy old film of the play.