Wave Engine, a game engine I covered here, just announced their 2016 developer contest with a $30,000 dollar prize pool, including $15,000 USD available to the first prize winner. The contest is sponsored by Plain Concepts and has a deadline that your game must be published to the Windows store by October 31st, 2016. They recommend that you make your submission by September 1st however. Other than needing to be 18, the requirement to publish to the Windows UWP store is certainly the biggest one. You are free to publish to other app stores and you are free to publish multiple titles for consideration.
Details on the actual contest are rather scarce. There is no set theme or requirement, simply make and publish a Windows 10 UWP game using Wave Engine. You can read the contest announcement here or watch the video below.