FreeCAD - An open-source parametric 3D modeler
Unity - The multiplatform game creation tools for everyone.
MakerSCAD - Powerfull 3D design tool for 3D printing, virtual reality and game engine.
Godot Engine - Feature-packed 2D and 3D open source game engine.
OpenSCAD - OpenSCAD is a software for creating solid 3D CAD objects.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.