Combination Weapons (5e Variant Rule)
From D&D Wiki
From the likes of the RWBY universe to the real world's pistol sword, multiple weapons combined into one have captured the hearts and minds of people everywhere, but filling up the 5e Weapons page with a combination of every weapon ever created is far too much. Enter this variant rule:
A combination weapon consists of two weapons that have been combined into one. Combination weapons have a weight equal to the heaviest weapon + half the weight of the lightest weapon. When you make an attack with a combined weapon, you may choose to make an attack with either weapon without interacting with objects to switch weapons. If either weapon has the two-handed or heavy property, the combined weapon does as well. If both weapons do not have the light property, the combined weapon does not. Not including the previous, each weapon benefits from its own properties when you make an attack with it.
- Buying and Creating
When buying a combination weapon, the item has a base cost equal to both weapons combined + 25% of the combined cost. A creature with proficiency in smith's tools can convert two individual weapons into a combination weapon for 25% of their combined values' worth of materials, or twice as much if done as a service.