Ahh yes! SMG's the perfect weapon for law enforcement under Close Quarter Battle conditions. Loved for their lightweight, accuracy, and low recoils. Perfect for combat situations where reflexes times are critical.
When SMG's are mentioned the MP5 comes to mind. With up to 120 diffrent variations and developed by German gun manufacturer Heckler & Koch.
MP5A4
MP5A5
These two guns fire 9x19mm ammunitions. They are extremely reliable and accurate. The two guns posesses diffrent stocks, the stock on the A5 could be extended for better support.
MP5K
MP5KPWD
The MP5K and MP5PWD are compact versions of the MP5A5. They're much lighter and perfect under situations when rifles are unmanagable. The PWD version has an attatched foldable stock.
UMP
The UMP is an extremely good choice of weapon when the additional firepower is needed. The gun comes in .40 caliber and .45 caliber variations. The UMP has a slower firerate compared the the MP5 in order to compensate for it's additional recoil.
UZI
The UZI is developed in several diffrent countries. It is loved for it's simplicity and realiability for being able to operate under harsh conditionds.
P90
My personal favorite SMG. Fed by 50 rounds ammo boxes. With an extremely moderenistic bullpup design. It uses 5.6x28mm ammunition. Developed in the Late 80's it's compact design, reliability and excelent ammo capacity makes it an excelent CQB weapon.