Volley gun
The Ribauldequin was a medieval version of the volley gun. It had its barrels set up in parallel. This early version was first employed during the Hundred Years' War by the army of Edward III of England, in 1339. Later on, the late Swiss army employed it.
Wax bullet
During the early 20th century, there was some interest in mock dueling with pistols loaded with wax bullets. The sport first gained popularity in France, and heavy canvas clothing was worn to protect the body, a metal helmet with a thick glass plate protected the head and face, and the pistols were often equipped with guards on the front of the trigger guard that extended outwards to protect the shooter's hand. For a brief time it was popular. It was featured as an associate (non-medal) event during the 1908 Summer Olympics in London.