WordNet (r) 3.0 (2006):

femme fatale
    n 1: a woman who is considered to be dangerously seductive [syn:
         enchantress, temptress, siren, Delilah, femme
         fatale]

Moby Thesaurus II by Grady Ward, 1.0:

35 Moby Thesaurus words for "femme fatale":
   Aspasia, Circe, Delilah, Don Juan, Jezebel, Lorelei, Messalina,
   Parthenope, Phryne, Siren, Thais, adventuress, charmer, coquette,
   courtesan, demimondaine, demimonde, demirep, enchanter,
   enchantress, enticer, flirt, harem girl, hetaera, houri, inveigler,
   odalisque, seducer, seductress, siren, teaser, tempter, temptress,
   vamp, vampire