Multi-platform Engine for Desktop, XBOX (UWP) and Mobile games
Cocos simplifies game creation and distribution with Cocos Creator
The game engine for everyone
3D C++ Game Engine - yet another open source game engine
2D Game Engine
The Atomic Game Engine is a multi-platform 2D and 3D engine
2D physics engine for games
TurboSphere is an easy to learn and powerful JS based game engine.