Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Sketch - Professional digital design for Mac.
FreeCAD - An open-source parametric 3D modeler
Affinity Designer - Professional creative software, exclusively for Mac.
Sculptris - Sculptris: Enter a world of digital art without barriers.