gimmick

(noun) a drawback or difficulty that is not readily evident. Synonyms: catch. Example: "It sounds good but what's the catch?."

(noun) something unspecified whose name is either forgotten or not known. Synonyms: doodad, doohickey, doojigger, gizmo, gismo, gubbins, thingamabob, thingumabob, thingmabob, thingamajig, thingumajig, thingmajig, thingummy, whatchamacallit, whatchamacallum, whatsis, widget. Examples: "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."

(noun) any clever maneuver. Synonyms: device, twist. Examples: "He would stoop to any device to win a point." "It was a great sales gimmick." "A cheap promotions gimmick for greedy businessmen."