The 501st Legion

The 501st Legion, also known as "Vader's Fist" during the Galactic Civil War, was a legion of elite clone troopers created by Supreme Chancellor Palpatine during the Clone Wars.
When Anakin Skywalker succumbed to the dark side and swore loyalty to Darth Sidious, the newly arisen Emperor assigned his apprentice the best the galaxy had to offer. For Vader's inaugural mission to raze the Jedi Temple, the Emperor provided him with a legion of elite clone troopers. Their distinctive blue-marked armor set them apart from the other ranks. Their crack marksmanship and coordinated team maneuvers allowed them to outflank the Jedi trapped in the Temple, and mercilessly gun them down. Though these clone troopers emerged from the smoldering Temple with their share of casualties -- some Jedi proved quite difficult to kill -- they were nonetheless successful in their mission.
The infamous legion is now under the command of Grand General Grahner Pol, who's campaigns against the New Republic have been steadily victorious for the Imperials. The 501st is led by the trooper GM-192, who's real name is currently unknown.
Current Members of the 501st
* GM-192 (Commander) (Gravik Kardo)
* GM-007 (Captain) (Beowulf)
* GM-016 (Captain) (Captain America)