KMASHI UV Flashlight, $6 with code GLVRLTE7

Blacklight flashlights are great if you want to spot hidden stains on train seats, hotel sheets, or (gasp) even in your own house...if that’s something you want to do.

It may seem silly, but if you find even one stain in a hotel room and complain to management, I guarantee that this thing will pay for itself several times over.