Is this a trope? Up for Grabs if it is. A subtrope of Mix-and-Match Weapon. Most guns consist of a long cylinder with a protrusion at one end. This basic shape can be quite similar to an axe, especially if the hand guard is unusually ornate. And thus, some characters wield weapons which can be used as either. Basically, a gun with a grip on the barrel and a bladed guard. Examples:
Hello, Unknown Troper. You'll need to get known to lend a hand here.