Sailors often refer to the CIWS as "R2-D2 with a hard on" due to its peculiar shape.
-Wikipedia article on Phalanx CIWS
I originally found out about it from a comment on Slashdot, where there was this additional little snippet:
Also, one of the things that makes this thing so kick ass is that once it decides to shoot something, it start shooting (at 4,500 rounds per minute (or 75/sec)) and the radar tracks each bullet's trajectory and corrects the aim based on that. It has eliminated any aiming error before the first bullet gets to the target.
-kryzx, Slashdot comment