Fortnite has released Update 17.21, adding a Plasma Cannon to the game. This new weapon can be found in regular and OP chests. It shoots huge balls of fire, which fly slowly, but demolish all destructible objects and equipment in their path, and also inflict considerable periodic damage to enemies.
This weapon fires no more than one plasma ball per shot. However, if you have several of them, then you can shoot several balls at once, switching between the guns. Of course, for this you have to sacrifice a slot in your inventory.
To craft a plasma cannon in OP, you need to combine a legendary pistol with an alien nanobot.