Unity - The multiplatform game creation tools for everyone.
HaxeFlixel - Create cross-platform games easier and free. All with one codebase.
Wick Editor - The Internet's free and open-source creation toolkit.
Game Guru - Create, play and share fun games on your PC with absolutely no technical knowledge needed!
Flixel Game Engine - Flixel is an open source game-making library that is completely free for personal or commercial use.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.