You might see the leader of a royal procession carrying a mace, or ceremonial staff. The word mace can also refer to two very different weapons: a long stick with spikes on the end or a chemical irritant that you spray in someone's eyes. Ouch!
Ever see a film about medieval knights battling one another? The spiked weapon that some knights used was called a mace — and it could put quite a dent in your skull. Because we’re all much more civilized now, we don’t use iron maces anymore, but police officers and riot police do use a chemical spray called Mace, which has much the same effect. It was invented in 1968, just in time to deal with pesky student agitators and the like. Get that in your eyes and it’ll ruin your day.