Firefox Reality - Mixed Reality for the Open Web
Catznip Second Life Viewer - Catznip is graphical client for Linden Lab's user created 3D virtual world, Second Life.
SteamVR - SteamVR is a suite of technologies created by Valve that power high-fidelity VR experiences.
Second Life Viewer - Download Second Life from the official site here.
VorpX - vorpX let’s you play your favorite games on Oculus Rift and HTC Vive in Stereo 3D. Many features are specifically tailored towards VR for the best possible experience on your VR headset.
Singularity Viewer - Singularity Viewer is a client program for Second Life.