Microsoft 3D Builder - View, capture, personalize, and print 3D models.
Autodesk DWG TrueView - Get a free DWG viewer to view, open, edit, and convert .dwg files, the native file format for AutoCAD files. DWG Trueview includes DWG TrueConvert.
Infurnia Architecture Design - Infurnia is a powerful, multi-featured cloud-native Architecture solution that you can use to introduce BIM in your Designs, partner up with others using functions, and take care of the data in an effective way.
Autodesk Design Review - Design Review lets you view, mark up, print, and track changes to 2D and 3D files.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
ZWCAD Viewer - Cross-Platform .DWG | .DXF | .DWT R12-2013 Viewer