"In modern role-playing games, the dodecahedron is often used as a twelve-sided die, one of the more common polyhedral dice" http://en.wikipedia.org/wiki/Dodecahedron
http://en.wikipedia.org/wiki/Dice#Non-cubical_dice
Even in the past, the dodecahedron was used for dice.
Here an example form the site archéologique de la Cathédrale Saint-Pierre de Genève
http://www.site-archeologique.ch/contenu.php?id-node=25&id-img=84
Copie d'un dé romain, en forme du dodécaèdre, datant du IVe siècle
Even older are the Etruscan dodecahedra:
More on the etruscan dodecahedron at sites:
