double dealer

from The Collaborative International Dictionary of English v.0.48

Double dealer \Dou"ble deal"er\, double-dealer \dou"ble-deal"er\
   One who practices double dealing; a deceitful, trickish
   person; a person who says one thing and does another.
   --L'Estrange.

   Syn: double-crosser, betrayer, traitor.
        [1913 Webster + WordNet 1.5] Double dealing

from Moby Thesaurus II by Grady Ward, 1.0

93 Moby Thesaurus words for "double dealer":
      Artful Dodger, Benedict Arnold, Brutus, Casanova, Don Juan, Judas,
      Judas Iscariot, Machiavel, Machiavelli, Machiavellian, Quisling,
      actor, archtraitor, bamboozler, befuddler, beguiler, betrayer,
      charmer, cockatrice, conniver, conspirator, conspirer, convict,
      counterfeiter, criminal, crook, deceiver, deluder, desperado,
      desperate criminal, dissembler, dissimulator, dodger, double agent,
      double-crosser, duper, enchanter, entrancer, faker, felon, fooler,
      forger, fugitive, gallows bird, gangster, gaolbird, gay deceiver,
      hoaxer, hypnotizer, informer, intrigant, intriguer, jailbird, jilt,
      jilter, joker, jokester, kidder, lawbreaker, leg-puller,
      machinator, mesmerizer, misleader, mobster, outlaw, plagiarist,
      plagiarizer, playactor, plotter, practical joker, public enemy,
      quisling, racketeer, ragger, rat, role-player, schemer, scofflaw,
      seducer, serpent, snake, spoofer, swindler, tease, teaser, thief,
      thug, timeserver, traitor, treasonist, trimmer, turncoat,
      two-timer