One of the things Microsoft announced during yesterday's livestreamed event was a new feature called Xbox Arena. With this, Xbox and PC players can create their own custom tournaments and invite their friends to play along.
There will be plenty of features like choosing if it should be a bracket, ladder or Swiss league (group play), or you can decide deadlines for participating, when it ends, and of course the competition rules. Arena will be launched for Xbox One and all Windows 10 formats next year for free.
What game will be the first you create a tournament for?