Messing around with another person's vehicle (ie: wrapping victims car in caution tape, filling one's car with trees and shrubbery, placing a skate ramp on top of a person's car, etc.) If no props are available one can sneak into someone's car and turn all the dials and switches so that when the owner starts the ignition, the entire car starts going crazy (ie: wipers at full speed, heat on full blast, radio on max volume, etc.) Also, car fagging can be performed on a moving vehicle (ie: passenger grabs the keys and turns the vehicle off while driving, passenger pulls emergency brake while on the highway, etc.)
Person 1: "Hey, why is your car wrapped in caution tape, was there a crime?"
Person 2: "No. That jackass down the street car fagged me."
Person 3: "Well, I guess we have to get him back. Time to go car fagging."