These colorful clown instruments are used by Gamzee to attack monsters. He has many of these clubs, and he attacks by juggling them one after another into the enemy's face. He apparently made it through the trolls' entire session without upgrading them even once, since he made friends with most of his Imps by giving them pie.
They are the
least most deadly pair of juggling clubs in the universe if they are in the hands of Gamzee.