Behold "the World's Most Irritating Instrument," a handmade noisemaker that has yet to find a single bid on its imminently-ending eBay action. From the description:
It makes a clicking sound that is varied by a turn of a knob. It has a momentary on/off button and a LED light that moves with the beat of the clicking. ... This is a One Of A Kind instrument by circuit bent artist MaXbEnDeR! Runs on a 9 volt battery
The auction lacks sample audio, which leaves us to speculate on exactly how accomplished Mr. MaXbEnDeR is at creating irritating noises. A search online does, however, suggest mastery of the genre. In any case, the seller's claim must be incorrect, because everyone knows that the world's most irritating instrument is the bagpipe.