If you're ever fortunate enough to play in the Majors for just a single game, cherish it, because you may not see another game. That's how it was with John LeRoy.
The Braves drafted LeRoy, a right-handed pitcher, in the 15th round of the 1993 draft. He eventually worked his way up to becoming the eighth-best prospect in the Braves' system in 1997. His numbers that year at Greenville were hardly spectacular (5.03 ERA in 98.1 IP), but was called up when rosters expanded in September.
LeRoy debuted September 26, 1997 at Shea Stadium against the Mets and worked two scoreless innings of relief. Not only did he strike out the side in his first inning, he was credited with the win. That's quite the debut. This was also memorable for being the Rafael Belliard home run game.
That was the only action LeRoy would see that year, or any year, at the major-league level. Two months after his debut, LeRoy was taken in the expansion draft by the Rays.
Unfortunately, his baseball career came to a tragic end. In 2001 as a member of the Sioux City Explorers, he suffered a heart attack and a brain aneurysm while rehabbing his pitching arm. He slipped into a coma on June 22 and died three days later at the age of 26.