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.
Sketch - Professional digital design for Mac.
TwistedBrush Pro Studio - A powerful and unique natural media painting program.
Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
Corel Painter - Corel Painter is media painting software.
Adobe Photoshop - Adobe Photoshop is a webtop application for editing images and photos online.