Tombstone Engine - A direct successor to the C4 engine.
Babylon.js - A complete JavaScript framework for building 3D games with HTML5, WebGL and Web Audio
PlayCanvas - PlayCanvas is an open-source game engine built on WebGL and WebVR.
Unreal Engine - Unreal Engine 4 is a suite of integrated tools for game developers to design and build games, simulations, and visualizations.
Armory3D - Armory 3D is a free and open source game development software developed using Haxe and Kha and made to run inside Blender.
Panda3D - Panda3D is a video game development engine and rendering software. It is developed and maintained by the Carnegie Mellon University Entertainment Technology Center.