For those who have everything: SpaceNavigator

Using a computer mouse seems so old-fashioned when you can use a SpaceNavigator. By reading hand movements, the PC controller removes the need for either mouse or keyboard and lets you “navigate virtual space in three dimensions.” A simple tilt of its top can control more than 100 3-D applications, including Google Earth or Second Life. Price: Starts at $59 Contact: 3Dconnexion.com
Source: Popular Mechanics