In the Aztec bonus mission, you can trick Jaws easily by leading him to the stairs room. He can't see past the sides of the stairs, as if there is a wall there. You can shoot him, and he moves, but he can't see or shoot at you unless he is on the same set of stairs as you.
The first level, Dam, was originally going to be bigger. Another part was in construction when the idea was abandoned. If you stand on the dock of the dam overlooking the water side and use the sniper riffle, it is possible to see another guard tower across the water in the distance. That is the unfinished part of the level.