A vanity license plate. It's like having a Twitter on your car, except you're limited to using 6 to 8 characters, you're stuck with the message for about a year, or have to pay immense fees to change the plate entirely, and you have the privilege of paying an extra $78 a year to retain that status on top of the initial $98 fee for getting the plate.
Believe it or not, despite the title, I'm actually a fan of vanity license plates. Primarily because it showcases one's creativity when restricted to 7 characters. That and it shows the lengths people will go to get attention, much like Twitter users.