Poorly shielded inductors in switch mode PSUs/old CRTs for me (Very common in older devices, low current causes the switching frequency to drop into the audible range.)

You can build your own tinnitus inducer with a cheapo 100kHz buck ic, put an air coil inductor on it, and then decrease the current until failure.

Let's also not forget the dreaded '... what do you mean I need to replace the batteries in my smoke detector?'

Though, I don't think you have to be autistic for that to be extremely annoying, lol.