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).
Cinema 4D - Cinema 4D is a 3D modeling, animation, motion graphics and rendering application.
A360 VIEWER - Free online CAD Viewer
Autodesk Maya - Maya is 3D computer animation software with powerful modeling, rendering, simulation, texturing, and animation tools for artists, modelers, and animators.
Glovius - Extensible & customizable 3D viewer, for consumption of product design data.