The Banshee is a large caliber Marauder handgun, which is also dual wieldable. It is typical of Maurader design as it is extremly powerful, and it can be used for anti-vehiclular operations.
Darius always dual-wields Banshee pistols. They have very good accuracy, and very high damager per shot. However, their fire rate is very low, and this, combined with its high accuracy, means that it is not good for bombarding groups of enemies or quickly turning and firing in an opponent's general direction.
Banshee Pistols are very effective at quickly dispatching light to medium armored enemies one by one at a medium to long range distance, and in order to use them effectively you must make sure that every shot counts. Damage is so high that Creepers can be killed in only two hits. Banshees are very precision-based weapons, and their effectiveness largely depends on how good of a shot their user is. While their damage is high and ammunition is plentiful, some of the more powerful weapons using rare ammo are better suited to dealing with the heaviest enemies in the game.