When an AF cop, I had a Presidential security detail at the USAF Academy.

While there, I talked to one of the men stationed there and he showed his nightstick that had been hollowed out for several inches and filled with lead. I suspect that it was very effective.

I was trained to use a nightstick at the Air Police School, but never saw a blackjack or sap on duty. Did see civilian cops with them.

Some people will grasp a roll of coins to give their fists added striking power.