Nice. I appreciate Xanatos Chess since my PC is pretty good at it. If you want a simpler, combat oriented, visceral fear, use Mike Pondsmith's answer to power monkeys.
First, have three goons for every PC. Nothing superhuman, just the kind of people that the PC's are used to slaughtering wholesale, all with Supersquirts. When the shots hit, nothing seems to happen immediately. (Perception rolls may apply to later rounds). About the time all of those guys go down, the acid rounds will really be doing a number on your PCs' armor. That alone should have everyone who doesn't have armor in their body getting ready to run. The next wave can use whatever you want but if you want fear, use gas. More accurately, use boxed text like this:
"Your armor is all but demolished. Wet drippy shreds hang from your shoulders but it doesn't look like it would stop a spitball, let alone a bullet. Anything that was previously sealed clearly isn't now. From around the corner you hear a distinct *FOOMP*, followed by several clangs as a grenade ricochets off the walls headed towards you. When the thick yellow gas starts spewing out of it, who is not running?"
