Epic Pen - A windows tool for drawing over your desktop and applications
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.
Adobe Photoshop - Adobe Photoshop is a webtop application for editing images and photos online.
PaintTool SAI - Learn to draw in different ways.
MyPaint - MyPaint is a fast, distraction-free, and easy painting tool for digital artists.
Gromit-MPX - Create annotations by directly drawing on your screen.