The 9mm Pistol (also called the 9mm Tactical) is the default firearm in Killing Floor. It is modelled after the M9 pistol. You begin the match with it in your inventory and it cannot be dropped or sold. It also has no weight.
It has a low damage, but a high rate of fire. It is not very accurate, however.
You can find or purchase a second 9mm to dual wield them, but the second pistol will have weight. You can sell the second pistol, but must always keep the original.
"A 9mm Pistol."