Blender - Blender is the open source, cross platform suite of tools for 3D creation.
STP Viewer - Free STP Viewer - free software that lets you view 3D STEP files (.stp, .step file format).
Autodesk 3DS Max - 3ds Max is software for 3D modeling, animation, rendering, and visualization. Create stunning game enrivonments, design visualizations, and virtual reality experiences.
A360 VIEWER - Free online CAD Viewer
ZBrush - ZBrush is a digital sculpting and painting software solution.
DXF View - A lightning-fast drawing viewer enables you to view DXF and DWG™ files on Mac