Checking paper currency for counterfeit,
Blood tracking (or is that 395nm?),
Urine spots,
Cleanliness of items (hotel comforters / sheets / upholstery),
Identifying uranium glass (or is that 395nm?)
Finding certain insects such as scorpions (any others?),
Finding minerals that fluoresce?
My recent acquisition of a Lumintop Tool 365nm UV light has aroused my curiosity. I'm much more likely to EDC it than my S2+ 365nm UV light.
slmjim
UV light does nothing with blood.
Cop tv series sometimes suggest otherwise, but that’s tv for you…
The neat thing about 365nm (and shorter wave lengths) is that it’s practically invisible so you don’t cast a purple light on the inspected objects.
I have 2 365nm lights.
The famous classic Nichia i have in a Singfire SF-348 (1× AAA) and a more powerful one (can’t remember the brand) in a black Romisen RC-A6 (2×AAA) which i only built recently.
Both with black lenses (ZWBA?) of course.
The benefits of these lights is that they have boost drivers, so no problems with Li-ion batteries running too low.
Oh, you can cure UV curing glues and paints with them too, but that also works (sometimes better) with 395nm.
But UV blocking glasses are recommended.
Not sure about the damage 365nm can do to human retinas, but it doesn’t feel pleasant to the eye.
By the way, you should try peeing with 365nm. 
Not done it myself but I believe UV used for tracing leaks using fluorescent dye, maybe in air-conditioning systems?
You can get ‘invisible’ UV ink for marking items for security tracking.
I’ve found lichen that fluoresces white-green.
UV also good for charging up glow in the dark items.
watch lume shots 
Blood stains need a dye, blood on it’s own, isn’t florescent.
Link to a webpage I found which mentions some brand names/chicals, if you’re interested.
Actually, similar to the fluorescent leak detection fluid, I suspect you can detect anything if you have a suitable florescent dye that will stick to the ‘thing’ you’re trying to detect, and not to the surroundings.
I remembered another “use” for UV- Professional “hand washing training” kits exist, where the “germs” are some kind of fluorescent dye applied to your hands. You wash your hands as normal, and the UV light will show where you missed.
With regards to other stuff to shine your lights at:
I’ve e seen fat/grease that has some moderate bluey green fluorescence under 365nm.
Also tonic water has a pretty good blue fluorescence.
LED emitters look cool under UV, too.
there used to be ‘tooth brushing discloser’ tablets
you would chew them, then brush normally
then look at w black light, to see where you did not brush
In the dark, dandelions appear brown amongst green grass. Poison oak also appears to fluoresce which is valuable to me.