A free VR surgery simulator. Probably not for the squeamish (though it's not like you'd see buckets of blood in it)

A friendly little village where you have to hunt out hidden objects. Some are merely in buildings, others are more hidden than that. Lots of interactive stuff to play with. Suitable for kids. Free

A game that's best enjoyed with room-scale movement. If you don't have a lot of space to move around, this won't be as immersive.

A free art museum filled with submitted art works. It's made pre-Index but works just fine (mostly). You won't see anything famous here but it's still nice.

VR Manga that lasts about 30 minutes but has no way to save your place so be prepared to sit through the whole thing in one go. No sound, no way to read at your own pace. Read a VN instead.

A free but older demonstration of Google's Resonance Audio SDK for spatial audio. I had to manually fix the floor with a separate utility but otherwise it works decently enough for the Valve Index.

A sequel of sorts to Boneworks, though really it's more of a mod platform sorta like garry's mod. There IS a game to play though, but it's not that exciting. Hopes are high for future content though.

A "gun sim" that is mostly focused on competitive shooting. For fans of USPSA style shooting ranges where you have to hit targets with limited number of rounds in the fastest time...