Unity - The multiplatform game creation tools for everyone.
Kodu Game Lab - Kodu lets kids create games on the PC and XBox via a simple visual programming language.
Godot Engine - Feature-packed 2D and 3D open source game engine.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
QICI Engine - Full-featured HTML5 game engine with visual interface for building games.
GDevelop - GDevelop is an open-source game making software designed to be used by everyone.