Atomic - The fastest way to design beautiful interactions
Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
Dotgrid - A simple vector illustration tool.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Invision - Prototyping and collaboration for design teams
Sculptris - Sculptris: Enter a world of digital art without barriers.