Spine - Spine is 2D animation software designed specifically for software and game development.
TwistedBrush Pro Studio - A powerful and unique natural media painting program.
Synfig Studio - Just another WordPress site
Adobe Sketch - Adobe Sketch lets users create expressive drawings anywhere using natural drawing tools like pencils, pens, markers and watercolour brushes.
Unity 2D - Unity 2D is a powerful and feature-rich game design solution built from the ground up to fulfill every basic and advanced need of the developer.
Corel Painter - Corel Painter is media painting software.