Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Sketch Mirror - Preview your iOS designs directly on your devices
Autodesk 3DS Max - 3ds Max is software for 3D modeling, animation, rendering, and visualization. Create stunning game enrivonments, design visualizations, and virtual reality experiences.
Flowkit - Sketch library for user flows/content maps/annotations
ZBrush - ZBrush is a digital sculpting and painting software solution.
Artrage - A simple but lovely natural media painting and sketching program.