This is an idea I’ve had floating around for a while. Stickers you can use to sabotage other people’s bumper stickers. This example is a sticker that says RST on it. You cover up the 4 on any Bush W’04 sticker and it changes it to WORST.
Another form of this would be one that you stick on someone’s SUV.
Of course I would never encourage anyone to actually do this since you could get charged with vandalism. That would just be terrible.