Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
MyPaint - MyPaint is a fast, distraction-free, and easy painting tool for digital artists.
Sketch - Professional digital design for Mac.
Microsoft Paint - Paint (formerly Paintbrush) is a simple, ultra-basic graphics painting program that is included...
Affinity Designer - Professional creative software, exclusively for Mac.
KolourPaint - KolourPaint is a free, easy-to-use paint program for KDE (a desktop environment for UNIX).