It has a name that sounds like 'slammer,' and that's a fair approximation of what it does! The SLAM-ER is a guided cruise missile, and is highly regarded within the Navy for its precision accuracy. It's not a Navy exclusive - all branches of the US armed force have access to it.
Each missile, which costs half a million dollars, can be remotely controlled in order to track and strike a moving target. They're made by aircraft manufacturer Boeing.