In the Exchange level to destroy that helicopter at the end, use that 
gun you got in the safe (Senteniel I think thats what it's called)and 
make sure you aim perfectly not to far up or down but side to side is 
okay. Shoot with that missle launcher and you won't be able to control 
it up and down but you will be able to control it from side to side. 
You have to hit it twice but you can still get hurt while your controlling 
the missle. 
Submitted by RobVG 76Chao