Level 1: Shoot both blue lights.
Level 2: Shoot out all of the upper
windows of the far back wall in the
Hangar.
Another can be found by shooting all
the yellow barrels when you are the
forklift.
Level 4: Shoot every yellow box
while you're riding on the STAAR
jeep
Level 5: Shoot the doorplate of the
second door marked General
Weatherby as the door is opening.
Level 7: Shoot all the yellow barrels
at the first area where the four purple
zombies are throwing barrels on the
hill.