Here is a picture of one of the trooper's holding a Remington 870 pump action shotgun. In the Counter Terrorist role these are primarily used for blowing hinges off doors but they can fire a number of different types of cartridge.
He is seen here wearing a helmet and headset, the helmet being important protection against falling debris. A respirator is worn to protect against the smoke from gas grenades thrown into the rooms to disorientate the terrorists.
Another important peice of equipment is the bullet proof vest giving the wearer protection against high velocity rounds. The overall colour scheme of the equipment is black for a very important reason, primarily designed as a shock tactic. Black figures crashing into a room cause fear thus gaining a couple seconds hesitation from the terrorist, just enough to kill before any fire is returned.
Just visible in the other hand is a Browning High Power, a 9mm hand gun with a formidable reputation.