Roger Clemens vs. Mike Piazza
Always a fiery competitor, Roger Clemens met his match in Mike Piazza. In an interleague game on July 8, 2000, Clemens beaned Piazza in the head with a fastball, resulting in a mild concussion that kept the catcher out of the ensuing All-Star Game. Piazza, who had gone deep off the Rocket in three straight games, said Clemens threw at him intentionally. The pair next met later that year in Game 2 of the World Series, and the feud boiled over -- in bizarre fashion. In the first inning Piazza hit a broken-bat-foul. The splintered barrel bounced toward Clemens, who scooped it up and threw it in Piazza's direction as he headed to first base. The two walked toward each other, and both benches emptied. Clemens later said he was tossing the bat to the ball boys near the on-deck circle. The Yankees went on to win Game 2 and the Series.