Over the centuries, two-fers have always been popular, in firearms as well as in other areas of endeavor. One of the odder combination weapons is a 16th century "gonne shield" ostensibly made for England's King Henry VIII's bodyguard. It consisted of a round shield about 18 inches in diameter, through which a breech-loading matchlock pistol protruded. The thought was that you could have an offensive and defensive arm all in one. Makes sense, but the only problem with the thing was, it was awkward as hell to use.
I had the chance to play with one a few years ago, and can attest to the fact that unless King Henry's guard was composed of a phalanx of octopuses, its almost impossible to manage easily, even under the most controlled circumstances. Too many things to have to do with too few hands. Interestingly enough there are a number of gonne shields still extant, so we can only assume that Hank Ocho, realizing their impracticality, stuck them away in the Tower and turned his attention to other more fun, practical things--like blowing off Pope Julius II, establishing the English Reformation and lopping off the heads of sundry spouses.