Just look for a small area in the wall that has metal grates on three sides. You can climb up one of the sides. The training man at the firing range at the Carrington Institute can be used as a human pincushion. Use poison dipped throwing knifes to throw out of the room. Just move to the position to shoot out of the range, use throwing knifes on him, and he will be a pincushion.
Double Death Turn on all weapons and infinite ammo.
Either turn on slow-motion single player or use combat boosts to slow down time. Shoot someone with a sedative arrow from the crossbow. While they're falling, use B to switch to instant kill arrows and shoot them again. They'll stop in midair and do another death animation. All you have to do is turn your X-Ray Scanner on right before the end of the level, as long as you complete the last objective or get to the end of the level with the scanner on.