I once made a neat maze design, using two exits that dropped down into two seperate mazes, each with a lever you need to pull, once you pull one, you need to go back through the first maze to get to the second, and then, you need to get to whichever of the two lower mazes has the door that leads out(which may be the one your not in), the original design also had monster spawners in the upper part, zombie sin this case, in order to make it easier to maneuver around the maze without having to be worried about getting swarmed or stuck. I also had ti set to dispense a few extra items back at the entrance to the upper maze, once you unlocked the doors, just in case you ended up going back to see if anythign had changed at the entrance.