Flail

A flail is a medieval weapon, a spiked ball attacked to a wooden pole by a chain. A form of club, although having fell out fashion due to the creation of firearms, Flails are still used in the Lowen Games and by Grimms.

Last Grimm Standing
While investigating the Lowen activities in the area, Nick found a flail in the weapons cabinet of the Trailer. Dimitri Skontos also often used a flails while fighting in the games. When facing Monroe, the two fought with Flails. Skontos proved to be the better fighter, but Nick intervened and took him on himself, the two also first fought with Flails. And Nick managed to best him in combat.

La Lloranna
Nick lent Moroe the same Flail he found last time he went looking for his Halloween decorations, which Moroe set up so it smashed a pumkinp every time someone pulled the doorbell. Later annoyed at him, some bullies turned it around so instead it smashed his window. He presumably gave the flail back to Nick.

Trivia

 * Although sometimes mistakenly referred to as a "Morning Star", the weapons shown are Flails, as a true Morning star is a spiked mace.