FreeCAD - An open-source parametric 3D modeler
Gombinoscope - Make and mix up faces
LibreCAD - An open source 2D CAD application for Windows, Apple and Linux.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
SketchUp - 3D for Everyone
Abrosoft FaceMixer - FaceMixer is designed to create fantastic face composites with multiple images.