This thread is about subtle, and easy ways to ruin someones day. This information isn't meant to be used against others, but rather to observe, and better understand the thinking, creativity, and thought-process of members who frequent this community. And remember, Turncoat is analyzing us all.
1. Pour sugar in their gas tank.
2. Post horrible things about them online for people who Google them to find later.
3. Login to their Wifi using their phone number, and change the password.
4. Login to their router using default credentials, lock them out, and change the password.
5. Place rusty nails in their driveway.
Stick both ends of a piece of wire in their outlet and blow their fuse
Fill a trashcan with water, tie it to their door handle, ring the bell and run off (even better if it already has trash in it)
To expand upon Luna's idea, break into their router with WPS or something and install a RAT on it that intercepts all of their passwords and shit
If you find anything interesting from doing that, then make some anonymous email account and threaten to tell their family and their employers and so on about it if they don't send you a shitload of money.
There's always the classic, order Mormon missionaries to their house. It really pisses people off lel
If they have a teenage-ish kid, get ahold of their phone number and then spoof a call from the school saying that they've been suspended for drugs or something.
Send them a bag of dicks. dicksbymail.com
Spray paint the sigil of Baphomet all over their house.
Yeah, that's all I can think of.