WordNet (r) 3.0 (2006):

antihero
    n 1: a protagonist who lacks the characteristics that would make
         him a hero (or her a heroine)

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "antihero":
   actor, antagonist, bit, bit part, cast, character, cue, fat part,
   feeder, heavy, hero, heroine, ingenue, lead, lead role,
   leading lady, leading man, leading woman, lines, part, person,
   personage, piece, protagonist, role, side, soubrette,
   straight part, supporting character, supporting role, title role,
   villain, walk-on, walking part