Good piece of information before the 2014 Sochi Olympics: the United States and Canada women's hockey teams absolutely HATE each other.
In October, the teams fought in their first of six pre-Olympics exhibitions. They played again Friday night in Grand Forks, North Dakota, and, well... with the USA up 4-1, all hell erupted right before the final horn in a line-brawl featuring international punching between everybody but the goalies. (Of course, the arena started playing the Rocky song.)
It kinda makes sense: three of the four women's hockey gold medal matches have been between the two countries, with Canada taking the last three. They're essentially the only countries that matter in the sport, and the players all know each other from their NCAA careers. If they're going to play in an exhibition match where fighting won't come with any real consequences, yeah, they're gonna get to brawlin'. (Oddly enough, men's international hockey doesn't typically feature fights like this.) We probably won't see this in the actual Olympics, but you know the bad blood is there.
Here's the fight from October, which is just as big: