Xash3D FWGS engine
The game engine for everyone
scene-oriented, flexible 3D engine (C++, Python, C#, Java)
Cocos simplifies game creation and distribution with Cocos Creator
New Godot bindings for Swift
Open source library for creative expression on the web, desktop, etc.
Urho3D Game engine
Multi-threaded game engine for Android
Modern AS3 Game Engine
Egret is a brand new open mobile game and application engine
2D physics engine for games
Cross-platform 2D game engine