Gmsh - Gmsh is a 3D finite element grid generator with a build-in CAD engine and post-processor.
FreeCAD - An open-source parametric 3D modeler
TetGen - A Quality Tetrahedral Mesh Generator and a 3D Delaunay Triangulator
SketchUp - 3D for Everyone
Altair - Visually Analyze Any Data at the Speed of Business
Blender - Blender is the open source, cross platform suite of tools for 3D creation.