Unity - The multiplatform game creation tools for everyone.
Coherent GT - Fast user interface runtime for PC and Consoles
Godot Engine - Feature-packed 2D and 3D open source game engine.
Sciter - Embeddable HTML/CSS/script engine
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Ultralight - Fast, light HTML UI solution for C++ apps