Your shtick is the particular gimmick or act you like to perform — it's your theme. After dinner parties, your shtick might be showing everyone your pet cobra.
A comedian or performer often has a shtick, which becomes the trick, song, or joke that people associate with her specifically. A clown's shtick could be falling flat on his back, and a pop star's shtick might be sticking out her tongue. In Yiddish, a shtik is "an act or gimmick," or sometimes "a trick or a prank." Literally, the word means "a little piece" or "a slice," from Middle High German stücke, "piece."