For females or even males there is always a chance of being attacked in a dark alley behind your favorite shady bar. This small and cheap ($13) gadget can trick the attacker into thinking you are prettying up for them when really they will just get a load of pepper spray in the eye.
I'm not sure how wise of an idea this is. A night full of drunken debauchery may hinder your ability to tell the difference between a spray nozzle and lipstick, eventually giving yourself a mouthful of pepper spray. Oh well, at least it will be useful for those three hours per day that you aren't drunk.