Heavy flail

Military two-handed melee weapon
Cost: 25 gp
Damage: 2d6
Proficient: +2
Weight: 10 lb.

This two-handed variation of a standard flail can bash through armor with ease.
Flail (Weapons in the flail group have a flexible material, usually a length of chain, between a solid handle and the damage-dealing end of the weapon.).

Published in Player's Handbook, page(s) 218, Mordenkainen's Magnificent Emporium, page(s) 21.