DVICE has a great slideshow on one of my favorite topics: weird guns! This is a hand mortar, one of the twelve featured oddities from the history of firearms:
Hailing from way back in the Musketeer days of the 1580s, these were hand-held weapons capable of delivering explosive ordinance that could have remained relevant all the way through World War I. Each measures 14" in length, with a 6 1/2" barrel capable of firing 2"-calibre grenades. For a soldier on foot, this was an immense amount of firepower to carry around, if only for one shot.
I want one. No, two.