The Jil UV or CR2 Ion UV use the nice-and-bright Cree 7090 UV LED. The Ion has 2 levels (kinda overkill for a UV light IMO) and is about 1/4" shorter than the Jil, but more expensive. The Jil isn't exactly cheap either, but it's quite a bit cheaper than the Ion. You'd probably get a better beam out of the Ion because the reflector is designed for it (I have an older Jil with the smooth reflector, and have to use a LDF lens to diffuse the beam).
The other option is a Photon. There's a violet one (405nm) and an ultraviolet one (370nm). I have both, and would reccomend the violet one for making things glow for fun. The UV one has a very short wavelength, nearly invisible beam. The nice thing is that it keeps everything surrounding the fluoresced object pure in color. The violet one has a greater "wow" effect because it's more visible. Comparing the two, I'd say violet one fluoresces things just a wee bit better than the UV one, even though the violet has a tendency to make everything purple, while the UV one gives better contrast. I carry a violet Photon Freedom on my keychain. A Photon 1 or 2 will probably work better since they can't be accidentally left constantly on (my Freedom, even on momentary, ocassionaly turns itself on to constant on), but they're not waterproof.
However, either Photon is pretty weak, and neither is as visible as you're going to want it to be. Under relatively bright fluorescent lighting (like a store or office) you can't see things very well. Stuff like the strip in a $5 bill or the seal on a driver's licence.
I'd carry my Jil on my keychain if it weren't so large (I already have a Ion Ti-XT taking up enough room, and another Ion would still be too much, not to mention confusing having 2 lights with the same body), but I still really want a brighter UV light than the Photon. I've asked Miller (of MillerMods) about a UV version of his Cree Arc AAA mod, which would be perfect for me if he's able and willing.
The Arc AAA and Peak Matterhorn were (still is for the Matterhorn?) available with a 5mm UV LED, and judging by how bright a white Photon is vs a white Arc, an Arc or Peak should work a bit better than a Photon (probably due entirely to the reflector), but any Cree-based one will blow these away.
