Cow bell.
Really? I’m surprised. The cello usually gets a lot of respect. Ok, the violin is the flashy star of the family but the cello is the cool older brother.
The viola on the other hand… Well, it’s the first instrument I thought of.
"Once there was a violist playing in the Winnipeg Symphony. He wasn’t that wonderful a player, so he sat at the back of the section. One day he was cleaning out his attic and discovered an old lamp. He gave it a rub and out popped a genie.
“For letting me out of my lamp I’ll grant you three wishes!” he said.
The violist thought for a moment and replied, “Make me a far better musician than I am now.”
The genie told him that this would be done. He was to go to sleep, and in the morning he would be a much better musician. The next day he woke up to find himself the principal violist of the Symphony. Well, this was just great, he thought! But he knew he could do better. He rubbed the lamp again, and out popped the genie.
“You have two more wishes!” he said.
“I want you to make me a better musician than I am even now!”
Once again, the genie told him to go to bed, and when he woke up it would be so. When the violist awoke, he found he was now the principal violist of the Berlin Philharmonic. Well, the violist thought this was pretty grand, but knew he could do better yet. He rubbed on the lamp again, and once more out came the genie.
“This is your last wish.” the genie said.
“I want you to make me yet a better musician still!”
Yet again, he was told to go to sleep. The next morning, he woke up to find himself back in Winnipeg, sitting in the last desk of the second violin section."
The accordion also has a bad reputation but it actually has a repertoire in classical music. Tchaïkovsky, Hindemith, Berg, Prokofiev, Shostakovich, Milhaud, Dutilleux and many lesser composers have written works which include it. Yes, accordion concertos are a thing.
I would never have thought of the banjo as the butt of jokes, though.
Tubas.
The thing I’ve noticed is that the instruments (not instrumentalists) most people seem to make fun of all have this twangy, whiny sound. The banjo, the accordion, the bagpipes, even the oboe. I think people just don’t like that sound.
Many mentions here, of bagpipes. I feel that this instrument gets an unfairly “bad rap” thanks to the great prominence, for whatever reason, of the Scottish version of the pipes, with their pretty-well-unique harsh and howling tones. In fact, there are other versions of the same instrument – found elsewhere in the British Isles, and in various parts of continental Europe – which have a far sweeter and more melodious sound.
That is like saying that Persian cats have a more melodic howl than Siamese cats when you step on them.
I’d beg to differ – would reckon, for instance, the Northumbrian bagpipes worlds different from, and much sweeter-sounding than, those of the Scots just “next door”; however, de gustibus…
If Bob Dylan comes to mind as cool, not sure what to say. The banjo is being “discovered” and used by more and more modern rock and Celtic bands, not to mention in a more traditional manner by cool new punk-influenced bluegrass, folk and country artists. Mumford & Sons, Flogging Molly and Dropkick Murphys use the banjo, as do Modest Mouse, The Gourds and others.
As for the harmonica, it’s OK, but pretty limited in what it can do. I always think of the weird guy playing guitar with a harmonica holder around his neck. Like Bob Dylan. 
I think you’re on to something: this kind of nasal quality can be grating.
Actually, the oboe has one of the most beautiful sounds… when played well. When played poorly it does indeed sound like someone trying to strangle two sick ducks at the same time.
Another example of violas being made fun of:
Larger than a violin but smaller than a cello
(for you old timey TV fans)
And the true answer to the question is the accordion.
I came in to mention Le Petomane as mentioned upthread.
Obviously, the butt of all musical jokes, especially around my family.
Apparently, he played an Ocarina and a rubber tube from his anus!
FTR, it’s Def Leppard.
Q: What’s the difference between an oboe and a bassoon?
A: You can hit a baseball a lot further with a bassoon.
My favourite band of the past two years, Public Service Broadcasting, love to throw it in now and again. And they are not even remotely bluegrass, folk or country.
I always told our french horn player to turn his chair around…
Any examples you could link to? Genuinely interested.
Depends on who’s playing it.
Two virtuosi:
John Sebastian Jr. (long after the Lovin’ Spoonful days)
https://www.youtube.com/watch?v=ADYFJhdrR2Q
and his father, John Sebastian (Sr.), who performed and recorded Classical harmonica.
https://www.youtube.com/watch?v=MH8JF0pm3GU
ETA: btw, Sebastian Junior is playing solo. That’s one person.
For Flanders and Swann, it was the French Horn:
I’m a computer-moron, and pushed for time right at present: but will gladly try, as soon as in less of a time-bind.
Re the above:
If the above fails to work: Google “Northumbrian Piper Andy May”: should deliver, second “hit” on the first page, YouTube video (8.48 mins.) of this guy playing.
I always had the impression that young violinists who weren’t quite cutting it were “encouraged” by band directors to try out the viola. Sort of the same way inadequate trumpet players get shuffled off to the baritone horn. Can’t kick 'em out of the band, so move them to where they can do less damage.
Only by people who don’t actually play the bass. The bass player can make or break a band. A good bass player can make an otherwise mediocre band sound good, and vice-versa. One problem that happens when a guitarist thinks he can just easily hop over to bass is that he doesn’t understand “groove” the way a dedicated bassist does.
I heard an old joke years ago about an all-female accordion band called “Ladies of Pain” 
Actually, the last I saw of Def Leppard, the bass player had retired, and rather than hire a new bassist, one of the guitarists switched to bass. So they’re a four-man now, unless they’ve since hired another member.
As a former bassoon player, I just had to share this one with my oboist friend 
ETA: Oh yeah:
Q: How many bass players does it take to change a light bulb?
A: Five. One to hold the bulb in the socket, and four to drink until the room spins.