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.
Ball and shot gun
The ball and shot gun was invented by COL George Fosbery, VC, who in 1885 took out the English patent (patent number 7565) for a system of very shallow rifling in the chokes of smoothbore shotgun barrels. Fosbery immediately offered the patent to Holland and Holland, who bought it and from 1886 until 1899, when the patent expired, had exclusive rights to build this class of firearm, marketing it as the Paradox gun.