Kodu Game Lab - Kodu lets kids create games on the PC and XBox via a simple visual programming language.
microStudio - microStudio is an all-in-one online game engine that enables you to create games, develop programming skills, have fun playing what you have created, share with others, and prototype.
Wick Editor - The Internet's free and open-source creation toolkit.
Godot Engine - Feature-packed 2D and 3D open source game engine.
QICI Engine - Full-featured HTML5 game engine with visual interface for building games.
ENIGMA – LateralGM - LateralGM is a powerful IDE for ENIGMA, and both of these combine to offer you a cross-platform game environment.