The phrase "unique gimmick" refers to a special or distinctive feature or trick that sets something apart from others in an interesting or attention-grabbing way. Full definition
This time, with someone who has a rather... unique gimmick for his channel. (gamingreinvented.com)
The bosses have their own unique gimmick, each feeling tremendously different from the last. (thevrgrid.com)
Players can task themselves to Knockout Challenge, play crazy tennis action with unique gimmicks like turning into Mega version of the characters, or keep things simple! (mariopartylegacy.com)