Once during the previous Bush's administration I saw a woman carrying a sign that said "BUSH -- stay out of mine."

Probably the funniest bumper sticker I ever saw, one that made me laugh out loud, was a variation on the "my other car is a porsche" bumper stickers that one oftens sees on junker cars. It read "my other car is a piece of shit too." It caught me off guard, and I think that's what made it so funny.