15. Head Six, 'Battlestar Galactica'
Or Cylons: It's Complicated. Played with smoldering menace by Tricia Helfer, "Head Six" was so named because she was the Six-model Cylon (the humanoid robots bent on exterminating humanity) who seemed to exist only in the head of sleazy scientist Gaius Baltar. Maybe she was a hallucination, induced by trauma or guilt over accidentally enabling humanity's partial demise. Or maybe she was some kind of cybernetic transmission who seduced him into triggering the apocalypse. Regardless, Head Six was of the great sci-fi allegory's big ideas about morality, loyalty, deception, technology, and spirituality, all wrapped up in a little red dress.