Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
Invision - Prototyping and collaboration for design teams
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Axure RP - The prototyping and specification software used by 87% of the Fortune 100. Beyond mockups, design interactive prototypes for business solutions, websites, and applications.
Cinema 4D - Cinema 4D is a 3D modeling, animation, motion graphics and rendering application.
UXpin - Design is really about solving problems. UXPin is the UX Design Platform that gets that right.