If you were a ghost, how would you haunt people?

Upgrade their PC to Windows 11 overnight
Click yes on all "recommended" options
Left-align taskbar and make it black
Restore their desktop wallpaper

You monster
- Had to be done
You're an evil person
Hope you brought install media, because it's a Linux system. And it doesn't have a TPM2, so Windows 11 might not even be installable.

So I guess I'm unhauntable.
- In that case, I'll switch you to Slackware.

I'm assuming that the haunting is because I had a vendetta against the haunted. In that case, I'd make their life miserable in the most subtle ways, including but not limited to:

Move their furniture half an inch at random so they keep stubbing their toes.
Make their clothing get stuck in doorhandles.
Loosen the knobs on their drawers.
Loosen the screws on the handles of their pots and pans by an eight of a turn.
Shift things in their cupboards so that something falls out every time they open them.
Damage the gaskets on their windows so that there's a draft and constant whistling sound.
Reopen their resealable packages a little bit so the food spoils faster.
Make their toilet leak, but only when they're sleeping.
Pack lint into their phone's charging port so that their charger never plugs in snugly.
Unbalance their appliances so they rattle/shake.
Slightly unbalance their car tires.
Loosen fasteners in their car so it produces annoying rattles.
Make their pens leak.

I would press the reset button of the modem constantly. Also disconnect the phone charger at night but connect it before they wake up so for some reason it only charged about 5%
The toilet leaking seems like a little too much effort for me, but otherwise I'm on board. Don't forget moving their small and easily misplaceable objects when they set them down. Maybe just around the room a little bit, like putting their phone on their seat when they get up instead of the arm of the chair where they left it.
No no, you make the toilet leak but only when they're sitting on it and scrolling their phones.

Playing with their pets while they're sleeping, by throwing small objects around the house.

...I wouldn't be a scary ghost but at least I'd have my fun.

Rile up the cat and lure it to attack the person's face while they sleep.
- That's evil. And fun.

I would constantly log them out of all their social and turn off their phone — what a naughty ghost would I be :p

Don't forget to delete the passwords saved in their browsers.

I wouldn’t. I’m a fucking ghost. I can just go about my day, knowing I’m a ghost, and not fuck with anyone.

You're gonna get bored after a while dude.
Yeah if anything I'd be a nuisance to the vampire and werewolf I'm living with!

My victims would never again find a matching pair of socks in their homes.

That's already my fiancee. I never have that problem - my socks are all identical.
- Maybe that's because he once wronged the wrong person who eventually passed away and now haunts him. ;)

I'll befriend and play with their cats. Their cats will do a zoomie randomly.

Ohh wait that's how a cat normally works.

I'll make their cat miao randomly.

Wait that's how they works as well.

I'll stand at a corner of the room, attract their attention and makes them looks like they stare at that corner for no reason.

Ohh that's how they works too.

Ohh well i'll just stick with making dogs bark randomly.

Ohh wait that's how dogs work too.

I would haunt scientists until somebody proves that ghosts are real.

Convince some kid that they have to spend a considerable amount of their lives, dedicated to figuring out why I'm here, and how they can figure out how to help me 'cross over'.

Then after a year or two I'd just get bored and tell them I made all of that up, and this is pretty much it. Then I'll go possess some guy to play videogames I guess.

Demand to know "are we there yet?" while haunting their house. Because of your going to haunt somebody and scare them, you might as well confuse the hell out of them too.

I would break the gas pipes so I would make the whole thing explode.

I don't quite know what the mechanism for this would be, but I imagine giving people random boners/getting them randomly turned on at times where its not appropriate would be quite funny. There are few mundane experiences which are quite so unpleasant as arousal when it shouldn't happen