15,000 shrieking tween girls at a boy band concert ( in this case New Kids on the Block plus 4-5 opening groups ). Okay that was more Cthulhu-level maddening than simply annoying, but it is easily the worst sound I’ve ever heard. Even with earplugs it was agony.
I would swear those girls had somehow mastered some fancy Yoga technique that allowed them to never pause to draw a breath. I can picture their wizened Yogi master exhorting them during their long training sessions - “breath through the nose, shriek through the mouth” ;).
Crinkling cellophane. Especially in a movie theater.
I tip my (noiseproof) hat to the mention of "people loudly eating food, especially on TV. Out here in Cali-land we used to have commercials for Carl’s Jr hamburger where they deliberately played up all the disgusting sounds of someone eating their messy burgers. I always wondered if those cost them more customers than they gained.
I third leaf blowers. And other noisy yard tools. Though for some reason, I don’t mind lawnmowers as much.
Also, those freaking idiots who drive their car around the neighbourhood really fast late at night during the summer, keeping me awake. It’s not so much that the sound of cars is annoying in and of itself, but I think it’s more the fact that they’re doing something annoying and dangerous.