Normally this wouldn't be a full size item, but this is a slow day so whatever. Something Awful has put up a guide on how to make a successful FPS. It's pretty funny, with over fifty(!) FPS staples. Here are a few favorites:

13. Enemy aliens often want to destroy the Earth because they've been driven insane from the flashing green and red colored lighting aboard their spacecrafts. All alien rooms and structures should have at least five light sources, each pulsating with a different bright color. This creates "atmosphere". 15. Bad guys, by nature, are real jerks. They should simply stand around and act like nothing has happened if their buddy, who was right next to them, is shot and killed. 50. Players should have some intense gravitational attraction either to or from ladders. Getting on or off them should be an incredibly complex task, second only to trying to swallow the Statue of Liberty.