1985: KANSAS CITY VS. ST. LOUIS
The National League won the All-Star Game 6-1 that season (played in the Metrodome, if you don't remember). But it was the American League's turn to host the World Series. So the Royals, trailing 3-2 in the series against the Cardinals, headed back home for Games 6 and 7. Kansas City trailed 1-0 in the bottom of the ninth before Don Denkinger's infamous blown call at first base, which led to a two-run rally, a victory, and eventually a Game 7 blowout win for the Royals. With home field reversed, that doesn't happen.
1986: BOSTON VS. N.Y. METS
The AL won the All-Star Game, but it was the NL's turn for home field in the World Series. Again, the team with that edge (the Mets) came back home trailing the series 3-2 and again needed a massive rally after the Red Sox went up 5-3 in the 10th inning of Game 6. What followed, of course, was a three-run rally -- helped by Bill Buckner's legendary error on Mookie Wilson's ground ball -- and the Mets went on to win the series. Again, that doesn't happen if the home field is reversed.
1987: TWINS VS. ST. LOUIS
One that hits close to home. The NL won the All-Star Game, but your beloved Twins, with 85 victories in the regular season, had the right to home-field advantage in the World Series. Both the Twins and Cardinals would use home field to the fullest advantage, with each winning all their home games. But it was the Twins who prevailed in the end at the Dome with the extra home game. Maybe the Cardinals would have won instead if current All-Star rules were in play?