Shortly after the discovery of radium in 1898 by Marie Curie and her husband Pierre, everyone wanted to put it in their products. Behold one of the strangest use of radioactivity ever: the radioactive radium chocolate! It was made by Burk & Braun, Germany, and sold from 1931 to 1936 for "its rejuvenation power."
More strange vintage products containing radium: Link [in French] - via Fogonazos, thanks Aberron!
Kind of like soy. :P