You haven’t lived until you’ve heard the massed pipe bands at a Scottish festival! 
Thanks for the link, ianzin. I always thought the vocoder was the device used by Peter Frampton (and many others) in the 70’s to get the “talking guitar” effect. Apparently not so!
I’m a lifelong guitar playing who’s gradually converting to lap steel guitar (both acoustic and electric), so I obviously love the instrument. But having taught beginners, I can attest that until you get the intonation right, it sounds really bad. Same with upright, or ‘bottleneck’ slide guitar.
Modern country music is only one application of the pedal steel guitar, and there it suffers from overuse and too many cliches. IMO, it sounds great in western swing and ‘sacred steel’ gospel.
Computers.
Laurie Anderson does fantastic stuff with a vocoder. I wouldn’t say that she’s my favourite artist but I do think she’s well worth listening to and has produced some truly memorable and enjoyable music with it. But that may be a matter of personal taste.
The dulcimer, especially when played by someone who doesn’t know how to play it.
The runner up is the Calliope. Once I had to take a ride on a riverboat on top of which was a calliope. It was August, I had a fever of 103, and that #&@ calliope blasted all through the stupid trip. It was enough to make an atheist believe in Hell.
Sitars are the most annoying S#$T I’ve ever heard.
And I don’t like Accordions, either.
Oddly, I do like Concertinas.
Bagpipes indoors.
Bagpipes sound better the further away they are - improving until they’re so far away, you can’t hear them at all, then they sound perfect.
OK< not really, but a lone piper heard at a distance can be quite evocative; a whole bunch of them marching around inside an office building 9don’t ask) sounds like the end of the world.
I’m a big fan of the sitar when used well. It doesn’t jibe with the vast majority of American music, but I really do love the way the Beatles put it to use on some of their songs.
Since when was the didgeridoo classified as an instrument? I mean really. I have a high tolerance for lots of off the beaten track and experimental musical sounds. Some of which were admittedly aquired tastes.
But as noted , most of the time someone really accomplished on any instrument listed above can at least do something interesting with it. But the didgeridoo proves wrong the admonishion that practice makes perfect.
The only thing worse would be some Tuvan throat singers backed by a didgerdoo orchestra.
Huh. Of the stuff listed, I don’t find them that annoying, and they all have their individual charms. (Although that might have something to do with the fact that I’m a big fan of the old school MIDI background musics from the SNES/early PS Square era.)
Does the human voice count as an instrument? I cringe whenever I listen to modern day singers belt out songs in a way that would totally ruin their vocal cords, or sound so breathy they could give Marilyn Monroe a run for her money. Doesn’t anyone get proper training anymore?
Makes you pine for the good old days of Ian Curtis, Johnny Rotten, and Nico, doesn’t it?
The holophonor, if you start thinking about neck-bolts.
Has humanity ever created anything more vile than the soprano saxophone? I swear, if Himmler played a musical instrument, it would have been soprano sax.
mm
What you’re thinking of is a “talk box.” It’s basically the bulb of a horn-style speaker connected to a piece of tubing to route amplifier output to the guitarist’s mouth. Easy enough to construct with one trip to Radio Shack and another to Home Depot.
My brutha!
Whatever it is that made the “wacca wacca chikka wacca” sound that made disco so annoying. It’s the same that sound permeated the porn industry during the '80s.
Was that a synthesizer?
The flute.
I could name some more less-used instruments, but of the more common instruments, I can’t freakin’ stand the flute.
I love organ music though (he says, the thread unread, but pretty sure this one will eventually be mentioned), especially the Flentrop organ at Harvard.
Mustn’t be many women reading this thread. I thought that duckbill speculum would receive most votes.
I have no knowlesdge of this so-called ‘porn industry’ of which you speak, but from your description and the reference to disco I think you are referring to the wah-wah pedal . Strictly speaking this is not an instrument as such, but an effect applied to the output of an instrument, usually but not always the electric guitar. I would have thought that perhaps the most famous/conspicuous example is the theme from Shaft, but the Wiki article I’ve linked to doesn’t mention it. It does mention a George Harrison song called Wah-wah from* All Things Must Pass*. I know the song and I don’t think it features a wah-wah pedal, or if it does it isn’t particularly noticeable.