Australia and the Underarm Bowl
While rugby is the national sport in New Zealand, in summer attention turns to cricket (comparable to Baseball in America, but with a running, overarm style of ball delivery). As with most sports for Kiwis, 
New Zealand’s greatest rivalry comes in the form of those bloody Australians and the most infamous sporting incident that has even happened between the two countries, happened in 1981 during the final of the World Series Cup.
On the last ball (pitch) of the Final match of the tournament, New Zealand needed to hit the ball out of the park to tie the game (very hard to do and very unlikely). The Australian bowler (pitcher) Trevor Chappell, brother of the captain of the team, bowled the last ball of the over (innings) underarm instead of the much faster and typical overarm bowl, thereby making it impossible to hit properly.
Naughty, naughty little Australians (still regarded as the lowest point in the long history of cricket). In Kiwi vernacular - "a lot of shit went down after that one" and still does to this day, almost 30 years later (a day would not go past in London where it does not come up in some Antipodean bar, somewhere).
The 30-second clip from YouTube below is as it was seen live on TV in NZ & Aus (watched, heartbreakingly, by most Kiwis who were alive at the time). To be fair, there ain't that many Australians out there who are chuffed about it either, when all is said and done.
From a personal point of view - a family friend of my parents threw his bottle of beer at the television in absolute disgust when this happened. He hit it square on and smashed the old style glass screen to bits. As a kid... I was tremendously impressed by this!