draw.io - Online diagramming application
Unity - The multiplatform game creation tools for everyone.
UMLGraph - UMLGraph is a professional automated drawing tool that allows the designers the declarative specification and drawing of UML class and sequence diagram.
Godot Engine - Feature-packed 2D and 3D open source game engine.
yEd - yEd is a free desktop application to quickly create, import, edit, and automatically arrange diagrams. It runs on Windows, Mac OS X, and Unix/Linux.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.