Gmsh - Gmsh is a 3D finite element grid generator with a build-in CAD engine and post-processor.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
TetGen - A Quality Tetrahedral Mesh Generator and a 3D Delaunay Triangulator
FreeCAD - An open-source parametric 3D modeler
meshmixer - meshmixer is an experimental 3D modeling tool for making 3D mashups without too much hassle.
ANSA - Product description of ANSA pre-processor of BETA CAE Systems.