The innocuous use of TV-B-Gone devices was to shut off at once all TV sets at malls; it was rather a prank than a destructive act, with the added benefit of getting some peace.
Back in the day you could turn a HP-48 into a universal remote control. Oh, the pranks we pulled on an unsuspecting teacher (the teacher was the worst kind ever of know-it-all prick, and duly deserved it).
Not that I know of, but technically doable since all it needs is transmitting through infrared the corresponding signal variants according to different brands. By modifying the source one could for example set all TVs to maximum volume, or tune them to channel 666, or even give different commands to different brands as they share the same IR codes.
