As a geologist/geophysicist we use UV lights a lot in the field. Very good for seeing the internal structure of carbonate rocks and looking for radioactive materials.
I strongly suggest you get a good one. I have 2 of them that I bought from Edmund Scientific.
http://scientificsonline.com/product...cd2=1156023654
They are expensive, but very nice. They have a lead acid battery so they can run for hours and have a built in charger. I have never worn out a bulb yet. You can switch from single bulb to dual or either bulb. I commonly have run mine for a complete night without the battery going dead. They also provide a power supply so you can use it at the lab during the day.
Finally, they are great to show the wife where the cat chucked on the carpet, and all of the other stains in the house. You can also track most spiders and bugs with them. They seem to fluoresce.