Casu marzu is an illegal Sardinian cheese that is served riddled with writhing maggots that try to jump into your eyeballs as you eat it.
Casu marzu is considered toxic when the maggots in the cheese have died. Because of this, only cheese in which the maggots are still alive is eaten. When the cheese has fermented enough, it is cut into thin strips and spread on moistened Sardinian flatbread (pane carasau), to be served with a strong red wine. Casu marzu is believed to be an aphrodisiac by local Sardinians. Because the larvae in the cheese can launch themselves for distances up to 15 centimetres (6 in) when disturbed, diners hold their hands above the sandwich to prevent the maggots from leaping into their eyes. Those who do not wish to eat live maggots place the cheese in a sealed paper bag. The maggots, starved for oxygen, writhe and jump in the bag, creating a "pitter-patter" sound. When the sounds subside, the maggots are dead and the cheese can be eaten.
(via William Gibson)