A mad suicidal gorge can do wonders, but it's all about psychological warfare. There's a chemical in EVERY marine's head (I think they put something in their nano-food) that makes them forget all else and go into a killing rage when they see a gorge. Something about that cute wiggly gorge butt fuels their blood drenched rage. A marine would cross hot burning coals and dance over the heads of an army of skulks, just to knife a gorgey. So, abuse that fact. Hang out with a skulk. Even if the skulk can't ambush very well, all he has to do is hang over a door or something and wait. When the marine comes by, have the gorge drop a chamber and start building it. That's the trigger for the marines. They say "AHHH GORGE, MUST SLAUGHTER WITH KNIFEY!" and go charging. Free skulk kill. Chuckle, healspray, repeat.