Goatse for people
For years people have been terrorizing unsuspecting internet users with the goatse image. The image is a real shocker and has the potential of sending you back into therapy, so google for it only if you are prepared to view the image.Goatse has spawned a whole new internet subculture with ASCII images and creative mutations of the images available all over (Warning: These sites are not work safe!), but Time magazine has given a whole new spin to it on its latest cover. (Intentional or not, is not for me to say).
For a work-safe description of the goatse image, and its history, check the wikipedia entry.
UPDATE: Goatse is all around you.. if you know how to look for it!