Pillow fights are one of those games that define youth. While it's rare to see pillow fights happening with adults, there are organizations that still play the game and take it very seriously.
Realistically anything can be made into a sport with some good regulation, but this game is particularly strange. The organization is called the All Japan Pillow Fighting Association and its members even came up with its own regulation pillows.
The sport is much like dodgeball in format except rather than running to the middle and picking the balls up, the players start off laying in bed. After the game begins players throw pillow at each other and block with their blankets. There are even referees to make sure when you're hit that you come out of the game. The game is strange but looks like a lot of fun.