Government inspectors use this X-ray gun to search imported food for metals and other contaminants. Nuclear nonproliferation inspectors use it to check cargo for illicit weapons components. Pull the trigger, and the gun emits X-ray waves. When the waves hit an object or substance, the object emits its own X-ray wave at a unique frequency that the gun can read. Number of guns sold in 2006: 2,000. Price: $25,000 to $40,000.