WordNet (r) 3.0 (2006):

gimmick
    n 1: a drawback or difficulty that is not readily evident; "it
         sounds good but what's the catch?" [syn: catch,
         gimmick]
    2: something unspecified whose name is either forgotten or not
       known; "she eased the ball-shaped doodad back into its
       socket"; "there may be some great new gizmo around the corner
       that you will want to use" [syn: doodad, doohickey,
       doojigger, gimmick, gizmo, gismo, gubbins,
       thingamabob, thingumabob, thingmabob, thingamajig,
       thingumajig, thingmajig, thingummy, whatchamacallit,
       whatchamacallum, whatsis, widget]
    3: any clever maneuver; "he would stoop to any device to win a
       point"; "it was a great sales gimmick"; "a cheap promotions
       gimmick for greedy businessmen" [syn: device, gimmick,
       twist]

Moby Thesaurus II by Grady Ward, 1.0:

195 Moby Thesaurus words for "gimmick":
   action, ad hoc measure, affair, anagnorisis, angle, answer,
   apparatus, architectonics, architecture, argument, art,
   artful dodge, article, artifact, artifice, atmosphere, background,
   bag of tricks, blind, bluff, bosey, catastrophe, catch,
   characterization, cheat, chicanery, chouse, color, complication,
   concern, conspiracy, continuity, contraption, contrivance,
   counterfeit, countermove, coup, course of action, craft, curve,
   curve-ball, cute trick, deceit, deception, demarche, denouement,
   design, development, device, dingus, dirty deal, dirty trick,
   dodge, dofunny, dohickey, dojigger, dojiggy, domajig, domajigger,
   doodad, dowhacky, effort, episode, eppes, etwas, expedient, fable,
   fake, fakement, falling action, fast deal, feint, fetch, ficelle,
   flumadiddle, fun, gadget, gambit, game, gigamaree, gimcrack, gizmo,
   googly, grift, hand tool, hickey, hocus-pocus, hook, hootenanny,
   hootmalalie, humbug, implement, imposture, improvisation, incident,
   instrument, intrigue, invention, jest, jigger, joker, juggle,
   jugglery, jury-rig, jury-rigged expedient, knavery, last expedient,
   last resort, last shift, line, little game, local color, makeshift,
   maneuver, material thing, means, measure, mechanical device,
   method, mood, motif, move, movement, mythos, object, pass,
   peripeteia, pis aller, plan, plot, ploy, power tool,
   precision tool, quelque chose, racket, recognition, red herring,
   resort, resource, rising action, ruse, scheme, scurvy trick,
   secondary plot, shake-up, shift, slant, sleight, sleight of hand,
   sleight-of-hand trick, snare, solution, something, speed tool,
   sport, step, stopgap, story, stratagem, strategy, stroke,
   stroke of policy, structure, subject, subplot, subterfuge, switch,
   tactic, temporary expedient, thematic development, theme, thing,
   thingum, thingumabob, thingumadad, thingumadoodle, thingumajig,
   thingumajigger, thingumaree, thingummy, tone, tool, topic, trap,
   trick, trickery, trump, twist, utensil, whatchy, widget, wile,
   wily device, working hypothesis, working proposition