Castle Game Engine - An open-source 3D/2D game engine for ObjectPascal.
Reality Factory - Reality Factory is a free suite of game development tools for building 3D games.
Open 3D Engine - Open 3D Engine is an open-source 3D game development engine in real-time.
CraftStudio - CraftStudio lets you craft games from scratch in real-time over the Internet.
Cyberix3D - Free online 3D Game Maker. Make your own 3D games online!
Limon Engine - Limon is a multi platform 3D game engine mainly focusing on first person games.