Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
Sculptris - Sculptris: Enter a world of digital art without barriers.
Sketch - Professional digital design for Mac.
ZBrush - ZBrush is a digital sculpting and painting software solution.
Adobe Illustrator - Adobe Illustrator is a vector graphics editor.