Quoting from another comment:

[...] pretty much all of them since the DK1 and a couple from the 90s.

• Rift DK1 (Kickstarter), Rift DK2, Rift Consumer w/ Touch
• PSVR
• Vive Pre, Vive Consumer
• OSVR variants
• Every Gear VR generation, excluding the current (don't really care about mobile VR right now and am passing on Daydream View for now)
• Tons of crappy Google Cardboard variants

Won't name my 90s HMDS to avoid potential for doxxing.

I recommend the Rift for development and general consumers due to the ergonomics (also PSVR here). Touch brings room scale and hand presence to Rift, so Rift/Vive are comparable at this point.

Valve is ahead on tech, better industry and consumer practices and OpenVR. Much prefer their efforts (Oculus loves console-like exclusives) and have a deep dislike for Facebook, but Oculus continues to do a great job on the user experience. Carmack and Abrash continue to push technical and philosophical boundaries.

Note that the Facebook tracks everything from these sensors and is able to recreate high fidelity behavior in any VR experience.

Not a surprise.