Wave Engine was born on February 21, 2013 with the exciting mission of developing an engine to help the mobile game developers’ community.
A lightweight engine for both 3d and 2d games that using c# as it's language. It is entity and component based and you can easily create your own components.
From version 2 it has a visual editor that helps in many ways.
One important flaw in my opinion is relatively small library and few built in components and it depends on the developer to make his\her components.
But this engine is growing consistently and effectively and I think in the near future it could be on of the first options of indie developers.
It comes with Occulus Rift now!! That's very impressive! Other than that its cross platform and its free. I love the fact that it is using C# as the development language and uses VS or Xamarin for its IDE. I hope to see more support/documentation though since I stumbled getting this to work on my laptop and didn't find any solution online but its all good now.
Good engine.