Gaming

If you want to dip your toes in VR (and have a Windows PC), get a used WMR headset. As mentioned in my other comment, a former Microsoft engineer made these usable again by releasing a custom driver after official support was removed from Windows.

These headsets all have high-res displays (perfect for flight sims and sim racing - you can easily read instrument panels), even the cheapest ones - and some higher-end models come with excellent OLED panels. Hardware requirements are very low and most PCVR games work just fine out of the box. Setup is incredibly quick and easy, with just a single cable with HDMI and USB at the other end (you also need a decent Bluetooth-adapter for the controllers). You can get one of these headsets - they were produced by a variety of manufacturers under license - connected and running in less than five minutes, including defining the borders of your play area. There's no breakout box, no adapters, no external trackers or additional power supplies.

Their main disadvantage are the somewhat clunky controllers that rely on camera-based tracking in combination with built-in sensors. Fine for quick movements everywhere and precise movements in front of the cameras, but the tracking is nowhere near as reliable as on more expensive or newer headsets (expect to briefly - a second or less - lose tracking about once every three or four hours of playing). It's still more than good enough for pretty much every VR game though, including the likes of Beat Saber, HL Alyx, competitive VR shooters, Skyrim VR (probably the best VR game there is), etc.

Controllers use standard AA batteries, by the way, which means there are no old and decaying built-in batteries to worry about. I'd get rechargeable ones.

Prices were incredibly low already compared to other headsets when they were new. Used - since most consider them obsolete after the official loss of support - they are a bargain. You can find a working Lenovo Explorer with controllers (the cheapest recommended option) for less than 100 bucks on ebay, easily. A fancier headset, like the Samsung Odyssey+ with its gorgeous OLED panel, can be had for maybe 20 or 30 bucks more. Do not buy these without controllers.

I would not claim that WMR headsets are or ever were the best there is in terms of VR hardware, but if you're just curious and want to get a taste of it and if you then want to casually play the occasional VR game, they are more than good enough for that.

Really important: DO NOT, under any circumstances, use the hinge to flip up the headset. The hinge is a weak point shared by all of these and it WILL break. Just take the entire headset off if you need to look around. Takes just as long and won't damage the fragile plastic hinge. Otherwise, these are very robust. I've smashed the controllers into walls, furniture and an unsuspecting family member without damaging them (and I've also bumped into stuff with the headset when I foolishly turned off boundaries - nothing happened).

All of them. Here's the driver:

https://store.steampowered.com/app/3824490/Oasis_Driver_for_Windows_Mixed_Reality/

Really the only downside is that Intel GPUs don't work. I modified the driver of my laptop's underpowered iGPU back in the day to get my Lenovo Explorer to work on it (just barely).

It's timestamped, skip to what you care about?

Edit: Here, I'll save you even that amount of effort. Battery Life Benchmarks (4 minutes, 30 seconds)