sticker

(noun) a small sharp-pointed tip resembling a spike on a stem or leaf. Synonyms: spine, thorn, prickle, pricker, spikelet.

(noun) an adhesive label. Synonyms: gummed label, paster.

(noun) a particularly difficult or baffling question or problem. Synonyms: poser, stumper, toughie.

(noun) a short knife with a pointed blade used for piercing or stabbing. Synonyms: dagger.