Shooter

Yeah, pull the trigger.

I didn't see any code in there for gathering mouse input so you must be looking for this:

If MouseDown(1) and Fire = False
  ;create a bullet (usually copy a bullet entity)
  ;point it in the camera's direction
  ;give it a velocity
  Fire = True
  FireTime = Millisecs()
EndIF
If Fire = True
  If Millisecs() > FireTime + 300 Then Fire = False
EndIf

I did a simple First Person Shooter code a few months ago. You can find it at my website here.