A mace was a type of hand-held melee weapon. Designed like a club, a mace had a spiked head attached to a handle.
On Rigel VII, this was one of the weapons available to a Kalar warrior. Unlike the pike and battle-axe, the mace didn't have decorative flourishes.
During his skirmish with one of these warriors in 2254, in an illusion created by the Talosians, Captain Christopher Pike chose this weapon over the pike. (TOS: "The Cage", "The Menagerie, Part II")
A mace was among the transmuted weapons created by the Beta XII-A entity aboard the USS Enterprise in 2268. (TOS: "Day of the Dove")