You mentioned it 2 posts above mine - how it not a part of the thread?
I agree with both of these. Runner up for Canada, particularly for the younger hockey fans is “Sidney Crosby, the Golden Goal!”
CFL: I’m not familiar enough with the history of the game to nominate anything older than a couple of years, but does the Thirteenth Man count as an individual (mis) play? Whoever it was…he’s famous for it!
While it was an exciting play, it was more a rescued airball than it was an ally-oop.
I agree with Warne’s ball of the century for cricket.
The thing which sets the Barbarian’s try ahead of all others for me is the nature of the Barbarians team. Here you have a festival team put together for this one match combining to create one of the most classic tries against perhaps the most legendary opponents in rugby. It’s like a cliched ‘plucky underdogs defeat the feared champions’ movie.
I STILL don’t know how he did that! 
minlokwat:
The Pine Tar Homer was in fact the game-winner.
And I’d say the most famous play in baseball history was Babe Ruth’s “called shot.” Whether or not you believe he really called it, he sure did hit it, and the legend of the call - true or false - made it famous.
In ice hockey, I’d have to say Stephane Matteau’s goal in 2nd overtime to put the Rangers past the Devils into the 1994 Stanley Cup. I will never forget Howie Rose’s call “MATTEAU! MATTEAU! MATTEAU!”
To clarify, Gonzo, I was equating “famous” with how many people have seen a particular event. In retrospect, probably an incorrect approach.
1.“We’ll see you tomorrow night!”
2.Another one I can’t figure out HOW he did it!
It’s a testament to Lomu that even though he retired sick, like, how many years ago, people still talk about him with awe. If I could mention a single standout play of his I would post it here, but pretty much everything he did in that World Cup was amazing. 'Cept in the final of course. 
Yep. Phi Slamma Jamma denied.
Not rectified in Houston B-Ball fans eyes until Hakeem beat Patrick in the NBA finals.
Wow. I watched the video three times and I’m still not sure how he did that.
This play by Ralph Sampson was very well known for a while.
NBA, Rockets vs Lakers
Most of the ones I can think of have already been mentioned. As someone that doesn’t really follow golf very much, I can only think of one golf “play”. That is probably a decent endorsement for it being one of the most famous plays in history.
Tiger Woods - Augusta National 2005 - 16th Hole
http://www.youtube.com/watch?v=0ZcpbsoeDZ0
In case you haven’t seen it, in 1999 ESPN put together a collection of clips called “Images of the Century.” Pretty awesome.
The only sports I feel qualified to talk about are college BB and baseball. For the NCAA I’d have to go with Laettner.
Baseball is a bit more difficult, but I’d have to vote for Bobby Thomson. All the others are probably as well known, but there is something about The Shot Heard Round The World that brings me unbridled joy. The Giants were a preseason favorite, but falter early and find themselves 13.5 games out of first place. Then they go an astounding 37-7 in the final 44 games to tie the Dodgers on the final day of the season, forcing a 3 game play-off to decide who will go on to face the Yankees in the World Series. They split the first two games, and all hope seems lost for the Giants when they enter the bottom of the 9th trailing 4-1. But they get back to back singles, a double, and ultimately a game ending, series ending Home Run that sends everyone at the Polo Grounds into a frenzy.
There was nothing special about the play itself. It was just a home run. But the phenomenal outburst of emotion surrounding the play is why we watch sports.
Also, his legs were so bad that he might not have been able to hobble to first on any ball that stayed in the park. It was a homer or nothing.
Ja, but that’s because he was poisoned, along with the rest of the team.
I actually nearly linked to that Lomu video as well but thought his demolition of England would only be well known in the UK and New Zealand.
For Rugby League, perhaps Martin Offiah running the full length of the Wembley pitch against Leeds in 1994 is a contender (though, again, I don’t know how well this try is known outside the UK).
And I still wonder if he switched hands to avoid a potential block (which is what Jordan says he was doing) or if he was just showing off.
late to the thread, so most of mine have already been mentioned (the Kirk Gibson homerun, the Tiger Woods chip-in at the 2005 Masters)
But as a converted Yankees fan (dating back to the drama of the 2001 World Series), here are my contributions:
Tino Martinez homerun in Game 4
Derek Jeter homerun to win Game 4 (as the clock ticked to November)
Scott Brosius homerun to tie Game 5
How they didn’t finish off the D-Backs in that World Series, I’ll never know.
Russ Hodges had the famous call, not Red Barber (although Barber did cover the game).
Apart from Hodges’ call, what made Thomson’s home run so memorable was the context. The Giants and Dodgers had the fiercest rivalry in American sports. The Giants had fallen thirteen and a half games behind the Dodgers by August 11. From that point forward the Giants outplayed the Dodgers, and the teams ended up tied at the end of the regular season. They played a three-game series to determine the National League championship (there were no divisions in those days - the team with the best record in the regular season won the pennant). The Giants won the first game and the Dodgers won the second. In the final game the Dodgers were leading in the bottom of the ninth inning when Thomson hit his famous home run.
It’s not just that Thomson hit a homer to win a playoff series. It’s that the homer capped a comeback by the Giants that took almost three months.