These throwing star magnets send the message that you mean business. The two rare-earth magnets hidden in the shortened point of each shuriken will stick them to any magnetic surface, such as refrigerators, cars, or some parts of your walls. They make a great gift for your ninja roommate. Available on amazon.
Update: There are also some awesome push pin shuriken.
Update: A throwing star coat hook.
Update: Wow, ninjas are going high tech fast! Below we have the USB shuriken. Now they can install their ninja rootkit from across the room with a flick of the wrist. (via CrunchGear)