Do you still have an old school modem on your computer? Set it up on repeat dial to his phone so it dials every minute or so. Then go to work, class, grocery store, home for the weekend.
Vaseline his entire windshield.
Wait til summer and take a dump in his hot car.
Run a wire from his car battery discreetly into the cabin. Leave an open ended wire barely sticking out of his car seat. Turns on the car...ZAP!
Rewire his car horn so it goes off all the time.
Slip a blowup doll into his passenger seat while he's at work.
Use the blowup doll first.