I carry a small IR signal disruptor called "Ninja remote" that allows me to turn off TVs in Walmart.
Most of the flatscreens Walmart sells are using a similar IR frequency, so by getting two or three of them set to the remote's hotkeys, I can casually stroll by the flatscreen row as and leave a trail of black screens behind me. I've creeped out a couple of employees that way, much to my amusement.
Also, if you (discreetly) shine a laser at a security camera, the monitor will look fuzzy and screwed up.

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