Tombstone Engine - A direct successor to the C4 engine.
Cyberix3D - Free online 3D Game Maker. Make your own 3D games online!
Babylon.js - A complete JavaScript framework for building 3D games with HTML5, WebGL and Web Audio
Castle Game Engine - An open-source 3D/2D game engine for ObjectPascal.
PlayCanvas - PlayCanvas is an open-source game engine built on WebGL and WebVR.
Unity - The multiplatform game creation tools for everyone.