The pronunciation of this weapon catches a lot of people off-guard. 'Phalanx' is easy enough, but the remainder of the name should be spoken as 'sea-whizz.' CIWS is an acronym for Close In Weapon System, and is used against missiles fired at ships.
Each Phalanx CIWS contains 20mm Vulcan cannons, and the system is fitted to all of the Navy's surface vessels. Some people think they look a bit like R2-D2 from 'Star Wars,' but the cute little robot was never this deadly.