FreeCAD is a general purpose feature-based, parametric 3D modeler for CAD, MCAD, CAx, CAE and PLM, aimed directly at mechanical engineering and product design but also fits a wider range of uses in engineering, such as architecture or other engineering specialties. It is a free and open source CAD editing application that's straightforward, reliable and portable.
Here are some screenshots to illustrate the features and user interface of this application:
3D Object Converter
Autodesk Fusion 360
ProfiCAD
VariCAD Viewer
Sweet Home 3D