In 2008, baseball historians commemorated the 100th anniversary of "Merkle's Boner". To everyone's relief, there was no sponsorship tie-in from Viagra or Cialis.
There is also Fred Snodgrass's "$30,000 Muff" in the 1912 World Series. It simply refers to a dropped fly ball in the bottom of the 10th inning by the New York Giants outfielder in the deciding game of the Series that eventually allowed the Boston Red Sox to win the game 3-2. $30,000 was the approximate difference between the shares given to the winners and losers of the Series that year.
"Muff" is still used today in football to described a mishandled kick or punt return.
The University of South Carolina's sports teams were originally called the Fighting Gamecocks, after South Carolina war hero Thomas "the Fighting Gamecock" Sumter. Over time, though, it's been shortened officially to "Gamecocks," and unofficially to fans and detractors alike as "Cocks." However, they appear to have wholly embraced the Double Entendre, as you can get shirts for the swimming/dive team that say "Wet Cocks Go Deeper," and see old ladies with bumper stickers saying "You Can't Beat Our Cocks!"
Americans, if you ever go to Australia, don't say you "root" for a sports team. Down here, "root" is slang for having sex. We barrack for sports teams.
Humorous writer Michael Green once accompanied an English rugby tour behind the Iron curtain, into communist Romania. He notes that the senior English dignitary accompanying the visitors realised he would have to make a speech at an official reception that night. Not knowing any Romanian, he reasoned that if he copied out the wording that appeared on the toilet doors, he would at least know the Romanian for Ladies and Gentlemen. He used these words to open his speech, and to his pleased surprise, it earned him a standing ovation from his hosts. He asked a Romanian rugby official afterwards, saying he was so pleased his speech had been received well, and the local smiled gravely. "Yes, Sir Henry. It does make you sit up straight when you are addressed as Urinals and Water Closets!
Rugby has a position called "Hooker", so named because it's the player that "Hooks" the ball with his feet and pushes it back to his teammates. Former hooker Brian Moore joked that it makes it difficult to travel when he tells the airport officials he is a professional hooker.
And we all snigger when the commentators say who is acting as first receiver.
New York Yankees relief pitcher Joe Page, who was, by all accounts straight, was dubbed "The Gay Reliever" during his heyday in the 1940s.
Lester Conner, who played point guard for several NBA teams in the '80s and '90s, had the unfortunate nickname "The Molester," because a) it rhymes with his name, and b) he played tough defense.
The University of Virginia's unofficial alma mater, "The Good Old Song" has been played for years at school football games after the team scores a touchdown. One of the lyrics is "We come from old Virginia/Where all is bright and gay", which means something very different now than when it was written in 1895. In recent years, students began yelling "not gay!" after this line until other students started protesting the obvious homophobia. So now they'll chant "Fuck Tech", a reference to their in-state rival, Virginia Tech, which apparently is supposed to be better.