We have one, but I have not used it very much. My daughter loves to go out with her metal detector, although I don’t think that she has found much of anything that was worth the time it took her to dig it out of the ground.
When I was growing up, my mom had an interesting device that had a purple light, ultraviolet, and it would pick up minerals in rocks, and change color.
We used to go camping a lot, and at night my mom and I would go out prowling around with the little ultraviolet light and find rocks that would fluoresce pink, green, or some other color. It was amazing how what looked like just a plain grey rock could have so many different minerals and change color in the purple light.
If I had one of those, I think that I would enjoy using it, and finding the fluorescent rocks, even though I have no idea what I would do with one after I found it.