Car horns, in most contexts, but especially the “I’m too lazy to get out of my car to ring the doorbell, so I’m going to sit out here in front of the house, laying on my horn until you get out.” I want to take a baseball bat to the cars of the inconsiderate bastards that do this in my neighborhood. Similarly, the guy who beeps exactly one picosecond after the light turns green. I wish I had a spring loaded sledgehammer mounted in my trunk just for this type of asshole.
I always feel like a cranky old curmudgeon, too, but the sound of children playing drives me crazy - it’s like as soon as they start moving, they start squealing and shrieking. The word “piercing” was invented for children’s squealing.
The hair on my arms stood up imagining this. 
I’ll nominate plain ol’ dogs barking for the worst sound I can think of - so loud, so annoying - always erratic, so you never know when the next volley is coming, and completely preventable.
My Macbook’s fan noise that starts up every time there’s anything video/moving image: it’s like a chainsaw sawing though my brain; I don’t remember being as annoyed with PC notebook fan noises.
This commercial: I can’t even take a nap with TV on: most annoying.
Random thuds of bass - inevitably of unidentifiable music as I can’t hear the rest - from neighbor’s woofers whether they be of TV, home theater sound system, stereo, car stereo.
Sound of someone clearing gurgling throat discharge (inevitably I also make the sound when I’m sick but just the same makes me gag).
Me too. I discovered I sound and talk exactly like one of my sibling that I never imagined I’d sound like.
I came in here to cite this one. Don’t know if it’s really a sound that doesn’t bother other people, per the OP, but it sure bothers me!
Agree with the phone ringing–I HATE talking on the phone, and whenever I hear it it throws me into a mini-rage. I even shout at it sometimes (when no one else is home) I hate it so much. The exception is when I’m expecting a call–then it’s okay.
Also agree with balloon-popping. There was a demonstration at my dad’s work once where a bunch of balloons were filled with different gases and then popped with a lit match on a stick. Some of them popped, others exploded with a loud BOOM. Scientifically it was a cool demonstration, but as a noise-sensitive little kid it sucked big time. If someone were to repeat it now I’d be appreciative of the scientific value, but I’d still cringe at the noise.
Alarms or warning sirens. I realize those are supposed to be annoying, but my hatred of them is utterly and completely visceral. Police sirens are tolerable (though loud), tornado/former air raid sirens creep me the hell out. The old fire alarm system at my elementary school was probably the worst–it had a deep growling sound that TERRIFIED me. When the school was remodeled when I was in about third grade, they changed the alarms to something a bit better-sounding, so fire drills no longer scared me.
As for other creepy or disturbing noises, my contribution is this. Not that I’m likely to hear it anytime soon, but it just gives me the willies.
Wow… that is pretty unearthly sound. Spookiness increases as I listen more.
Nose blowing. I’ve never understood why it seems to be socially acceptable to place a rag up to ones nose and honk away.
Enhanced bass systems in cars.
My mother
In this vein - I hate the sound of a baby breastfeeding. I know it’s politically incorrect and all, and in theory I have nothing against the idea of public breastfeeding. But I dread seeing people breastfeed - not because of the sight of boobies, but because I know that wet, slurpy, snuffly sound is coming. A baby drinking from a bottle isn’t great either, but it doesn’t seem to be nearly as bad.
Frankly, I could do without watching young kids eat too, but that sound…ewww.
I haven’t heard the sound since I was a kid, but the high pitched wailing of snails cooking in butter and garlic in the frying pan.
Are they screaming?! I dunno? Is it just the sound their sizzling slug bodies make? I dunno… All I know is it must sound like what Obi Wan heard when Alderaan blew up.
I can’t live without it now (garlic, not snails), but that sound associated with the smell of garlic used to make me recoil and hide under the furniture.
And no, I’ve never even tried escargot/fried snails. ::shudder::
FYI, I’ll be stealing that.
Babies screaming, definitely, especially if it’s a pain cry.
My weird sound aversion is the clapping at golf tournaments on tv. It’s this weird, muffled sound. It really gets on my nerves.
the sound of the bone in my right big toe spiral-fracturing in two places when i landed on it after falling down the stairs. ow, ow, ow and ow!!! :eek:
overtired children and/or infants screaming at full volume in the next aisle at (insert retail store of your choice here).
that knife through the styrofoam thing? i actually squirmed in my seat when i read that. :eek::eek:
tendons snapping over the joint. doesn’t hurt, but it’s as bad as the knife/styrofoam.
leafblowers. I hate, hate, hate that sound.
Oh “GO IN THE HOLE!!!” screams get under my skin. Only times when it’s remotely tolerable is when the ball is actually rolling towards the hole on the green.
My husband has the loudest, most piercing nose-blowing in the world. I actually have to plug my ears when he’s blowing his nose. And he has allergies, and blows his nose ALL THE TIME.
The noise the BART makes when it picks up speed. It’s this high whine that sounds very much like the noise in Manfred Mann’s “Blinded By The Light”, (~ 1:12 here), only much much higher and louder.
If I don’t have headphones on I have to concentrate or I’ll start behaving like Rainman when he thinks he’s boarding that Qantas flight.
When a broom or mop or other similarly long handled device falls on the floor and makes that high pitched slapping sound. That literally hurts my ears.
ETA: Morbo, I love that sound!
I way prefer nose blowing to sniffing. I know someone who sniffs about every 17.5 seconds. One day I will snap and murder her.
I also hate any children singing in songs. It just wrecks the song. Don’t do it.
I had heard that rabbits made a horrid scream but always thought it was bunk until I actually heard it. Friend of mine had a rabbit hutch when I was a teenager and I was visiting one day while his dad was cleaning the cage. Rabbit managed to get loose, had encounter with neighbor’s dog. A truly terrifying sound.
I’ve heard that deer make a similar sound when facing death. I’ve never heard it in person, hunters I know say they’ve never heard a deer scream.