Declare your apartment an independent nation, and sue your neighbors upstairs for "violating your airspace".
Honk and wave to strangers.
At the laundromat, use one dryer for each of your socks.
Deliberately hum songs that will remain lodged in co-workers brains, such as "Feliz Navidad", the Archies "Sugar" or the Mr. Rogers theme song.
Sit in your front yard pointing a hair dryer at passing cars to see if they slow down.