Polybius

Polybius is an urban legend about a rare arcade game released in 1981. The game was created by a mysterious company called Sinneslöschen and was a puzzle/shoot-'em-up somewhat like Tempest. It was only released in a few suburbs of Portland, Oregon. It supposedly did very well, with people forming long lines to play it. However, it was said that players would eventually have nightmares or even develop amnesia. Some even committed suicide. Others stopped playing video games altogether and at least one became an anti-video game activist.

According to one owner of an arcade, men wearing black suits would often come to collect "records" from the game. They did not take any money, simply data on gameplay. Because of this, the leading theory is that it was some sort of government experiment using subliminal messages. The game remains in obscurity as around one month after its release, all of the cabinets suddenly disappeared. While some have tried to recreate it, no one has ever found the original ROM.