CAPRICA SIX, SHARON ''BOOMER'' AGATHON, AND D'ANNA BIERS (Tricia Helfer, Grace Park, and Lucy Lawless)
in Battlestar Galactica (2004-present)

Cerebral villainy just doesn't get any hotter than this robotic trio, who have been vexing humanity since their fellow Cylons wiped out mankind in an all-out war. (Okay, maybe Boomer isn't a complete villain...but she has done some very bad things.)