Another one:
Standalone - A Shopping Trip to Eklan Tor - amazing little game, very cool experience for someone new to VR. Simple low-poly graphics, but a very intricate little interactive environment for someone to explore in VR, like a very elaborate doll house or doll village. I've always been fascinated with miniatures, so it's right up my alley. The controllers displayed in the game are a bit messed up and I noticed some aliasing or something (it may just be my settings, I need to check the articles/videos for the ideal settings) but it's still very much worth it.
The three that I've listed so far (Arcturus Vision, BoomXR, and Eklan Tor) seem like very good free options to demonstrate VR to someone. None of them have any locomotion, so it should keep any chance of VR sickness to a minimum if not eliminate it completely.