Lots of things fluoresce. You could find teeth or bones, various minerals, cleaning product smears, petroleum based cosmetic smears, some diamonds and other gems, soaps, secret memos, enough to keep you and the "lab" busy for days. Happy hunting...

Oh, you may want to invest in a UV source that emits short wave UV as well as long wave UV. Some items only fluoresce under one or the other, or emit a different visible spectrum color under each. Thats what I remember from my science fair project...