In the Silent Cartographer (Level) there is a glitch that makes marines freeze, and you will be able go through them. First take a Warthog and fill it with marines. Second, take the Warthog to the door you are supposed to open, and leave. Then you are going to open the door. Once that's done, go to the door again, and ask the marines to step out. If you've done it right so far, they should still sit there. Go out and get a new Warthog and drive back there. Now the marines should be out. Now hit them with the new Warthog, and their weapons will fly out of them! they will just stand there and be like ghosts. But if you activate the Silent Cartographer, they will dissappear.