Friendship Breaking Games
I saw the following image on my Facebook feed:

All I could think when I saw it was that they haven't played Risk. I'm not sure what type of friendships are broken due to Uno or Mario Kart; they must be weak definitions of friendships (probably acquaintances). I can see Monopoly damaging relationships but that game is too much luck for one to be too serious about that game. Goldeneye was just a good game filled with fun moments (though I prefer Perfect Dark). To be honest, I'm saddened by the fact that split screen gameplay has nearly become a thing of the past.
Risk is just naturally a hostile game. Alliances are bound to form (well, at least if you want better chances to win). And with the long duration of the game (unlike the games in the image above), it increasingly become more invested with winning. You don't want hours of gameplay to go towards a loss.
I can't wait to play Diplomacy. From what I have seen/heard, it's a more intense version of Risk, which includes more negotiations and planning. But I assume that those who play such a game have formed a mentality to not let what happens in the game affect their friendships. Unfortunately, this is not the case for everyone.