First of all, while it may make me sound like a conspiracy nut, I believe that some countries have already developed and deployed real-life cloaking devices, but each country's military has kept it under wraps. It makes sense, to me at least, for any military to keep their cutting edge tech as secret as possible for as long as possible (look how long it took for the U.S. government to reveal the stealth bomber).
As for the question, I'd use the cloaking device to trip loud, screaming kids running through grocery stores and in jack-ass that goes around in heelies (I despise that fucking shoe). I would also use it to frame people I don't like for shoplifting and I might use it to shop-lift things for myself.
Finally I'd use it to make people think that they're going crazy, like whispering in their ear, moving things when they're not looking and changing the t.v. or radio channel on them.