Grit Game Engine - The Grit Game Engine is an MIT-Licensed Open Source Game Engine that is highly scriptable via Lua.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Pygame - Pygame is a set of Python modules designed for writing games.
MakeHuman - MakeHuman is a free, open source, interactive modeling tool for creating custom 3D human characters.
Bforartists - Bforartists is a fork of Blender.
Unigine - Unigine Engine is a proprietary cross-platform middleware, developed by Unigine Corp.