Castle Game Engine - An open-source 3D/2D game engine for ObjectPascal.
Open 3D Engine - Open 3D Engine is an open-source 3D game development engine in real-time.
Godot Engine - Feature-packed 2D and 3D open source game engine.
Unity - The multiplatform game creation tools for everyone.
PlayCanvas - PlayCanvas is an open-source game engine built on WebGL and WebVR.
Cafu Engine - A game and graphics engine for multiplayer, cross-platform, real-time 3D action, GPL licensed