Blender - Blender is the open source, cross platform suite of tools for 3D creation.
FreeCAD - An open-source parametric 3D modeler
OpenSCAD - OpenSCAD is a software for creating solid 3D CAD objects.
Sculptris - Sculptris: Enter a world of digital art without barriers.
Autodesk AutoCAD - Autodesk AutoCAD is a commercial computer-aided design (CAD) and drafting software application.
meshmixer - meshmixer is an experimental 3D modeling tool for making 3D mashups without too much hassle.