In  the "hardline.cfg" file, enter the following line at the end.
It's  case  sensitive,  so  type  it  exactly  as  shown:  CHEATING IS
SOMETIMES USEFUL BUT FOR HOW LONG ???

Now during the game hit the following keys:


X-Invincibility 
BACKSPACE -Kill all enemies on screen 
HOME -Gain main weapon ammo 
INSERT-Full health 
PAGE UP-Gain accessory weapon ammo