Sports strikes are famous due to the large sums of money that are negotiated. In some sports, entire seasons were canceled because both sides could not reach an agreement in time.
In 1987, the National Football League Players' Association called a strike over free agency (a player's right to sign a contract with whatever team he wants). The players walked off the job two games into the season, and three games were played by players recruited from colleges and other football leagues. Scab football was extremely unpopular, and a few NFL regulars crossed the picket lines to resume play. Players continued to return to work until the strike ended without any resolution. Eventually a new contract was signed that was more to the owners' liking [ref].
In 1994, the Major League Baseball Players Association refused to accept the owners' demands for a salary cap. The season ground to a halt on August 12, 1994 and the World Series was cancelled. It was the eighth baseball strike in history, and the first time that a North American professional sports organization postseason was lost because of labor disputes. Play resumed again in spring 1995 under the terms of the expired contract, after a judge issued an injunction against the team owners [ref].
Although there have been three work stoppages in National Hockey League history, only one of them was a strike. In 1992, hockey players went on strike for 10 days before reaching an agreement with owners. The 1994 and 2004 work stoppages were lockouts -- the employers' counterpart to a strike. The owners prevented the players from returning to work when they could not come to an agreement. The 2004 lockout lasted an entire season, making the NHL the first North American sports organization to lose an entire season to a labor dispute. It was also the first time since 1919 that the Stanley Cup went unawarded [ref].