An instrument being judged by how many twits play it badly? What kind of measurement is that? I'd rather consider whether an instrument can be played at all as the measure of its "worstness." One that comes to mind is the ukelin, actually a bowed psaltery. I have heard bowed psalteries, and none of them sound good (the worst of them sound, well, worse). But the point on the string where the bow of a bowed psaltery touches the string is so close to the end point of the string (think: bridge) that good tone is absolutely impossible.

In 1876, at the Centennial Exposition, thousands of musical instruments were submitted for prizes, and one, despite repeated appeals and re-entries, never managed to "pass." It was a bowed PIANO! I suspect it had some kind of mechanism to bow each string, said mechanism somehow controlled by a keyboard, so it would have been a mechanized (for you Brits, mechanised) bowed psaltery. I suspect it would have been the world's worst instrument.

Many of the other autoharpish instruments produced by the Marx company (they made the ukelin) like the Marxophone, Hawaiian Tremoloa, et al, could actually play tunes, and probably were acceptable, if not automatically accorded ne plus ultra status.

But guitars, even electrics? Banjos, even guitar banjos? They're not "good" or "bad," since they can be played to good effect. It's the ones that no one can play well, those are the "worst."

Bob

(and I didn't even mention the Humanotone, a plastic gizmo that qualifies as a nose flute of sorts).

(Oh, and the slide whistle! Now there's a sound that's hard to put up with, even if played well, which isn't often.)