LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
Unity - The multiplatform game creation tools for everyone.
QCAD - QCAD is an application for computer aided drafting in 2D.
Godot Engine - Feature-packed 2D and 3D open source game engine.
FreeCAD - An open-source parametric 3D modeler
Blender - Blender is the open source, cross platform suite of tools for 3D creation.