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.
Aseprite - Aseprite is an art program dedicated to the creation of pixel art.
Autodesk SketchBook - SketchBook drawing and painting software provides designers, architects, and concept artists the tools to sketch ideas quickly and create beautiful illustrations.
Pixel Studio - The Pixel Art Is Always Fun
Clip Studio Paint - The artist's software for drawing and painting.
Piskel - Piskel is a website where designers online create sprites or pixel art.