Been to the video store lately? Games rated "Mature" (17 and older) and "Adults Only" crowd the shelves within your young teen's reach. Take "Manhunt." It lets a player "become" James Earl Cash, a serial killer. A character named the Director wants to use Cash in snuff films. As Cash, you slaughter people. You slice them with a chain saw, behead them or stab them viciously in the eyeballs. Meanwhile, the Director adds his comments: "You're really getting me off, Cash" and "You're really doing it for me. Why I ain't been this turned on since ... Well, let's not...