Cyberix3D - Free online 3D Game Maker. Make your own 3D games online!
Unity - The multiplatform game creation tools for everyone.
Open 3D Engine - Open 3D Engine is an open-source 3D game development engine in real-time.
LOVE 2D - Hi there! LÖVE is an *awesome* framework you can use to make 2D games in Lua.
Castle Game Engine - An open-source 3D/2D game engine for ObjectPascal.
Pygame - Pygame is a set of Python modules designed for writing games.