GIMP - GIMP is a multiplatform photo manipulation tool.
LinuxCNC (the Enhanced Machine Control) - LinuxCNC: an open source CNC machine controller. It can drive milling machines, lathes, 3d printers, laser cutters, plasma cutters, robot arms, hexapods, and more.
Krita - Krita is a professional FREE and open source painting program. It is made by artists that want to seaffordable art tools for everyone. Concept art. texture and matte painters, illustrations and comics.
Vectric Aspire - The complete software solution for CNC Routing,
MyPaint - MyPaint is a fast, distraction-free, and easy painting tool for digital artists.
Mastercam - Mastercam's Dynamic Milling is a game changer for us.