Whew, things are moving fast. So 3MF Viewer is now live on the Mac App Store and I've got a few more lined up to join it. The 3D File Viewers suite has been expanded to support MagicaVoxel (.vox) and the DXF format.
On a similar vein, I've started publishing some dataset viewers for macOS - starting with a fast SQLite viewer, and expanded to include Microsoft Access db as well as GeoPackage (.gpkg). Ready for download from here and hopefully on the Mac App Store soon.
Note: I have removed the Combined 3D File viewer from this site - it is now only available from the Mac App Store - this is mainly because it is getting updated regularly (new formats, bug fixes etc.) and so distributing via the App Store is the best way. The small fee does help keep me creating, though!
As ever, feedback, comments and feature requests are warmly received.