Most of the parts used are from the new NXT and original RCX Mindstorms sets.  However you may need some extra parts in order to build this robot.  Extra components can be purchased through the Lego store ,Lego education store or number of other Lego online vendors. 

This robot can be programmed to move around and rapid-fire 5 rounds.

NXT Gunner-bot alignment:

The proper positioning of the hammer to the bullet is critical and could take few tries to find the optimal position.  The adjustment is easy.  Pull back the tensioned lever at the back of the gun and then turn the gun barrel until the bullet is aligned directly in front of the hammer and then lower the lever back down until gears are engaged. Now try running the motor

caution! the large gear attached to the hammer should turn in counter clockwise direction only.