Figma - Team-based interface design, Figma lets you collaborate on designs in real time.
Spine - Spine is 2D animation software designed specifically for software and game development.
Sketch - Professional digital design for Mac.
Synfig Studio - Just another WordPress site
Invision - Prototyping and collaboration for design teams
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.