Emperor's Personal Guard

The Emperor's Personal Guard was a Dalek organisation made up of Daleks dedicated to protecting the Emperor Dalek at all costs. They were normal Daleks, but with black domes; in addition, they sometimes possessed claws instead of standard manipulator arms or more powerful gunsticks opposite the standard.

History
For whatever reason, either as the Emperor's commanders or simply for their superiority, there were at least two Personal Guard in the execution party that chased the Doctor's TARDIS through eternity. (TV: The Chase)

The Emperor was always guarded by the personal guard in its throne room on Skaro. Their dedication to protecting the Emperor may have superseded their obedience, as they protected the Emperor from the attacking Humanised Daleks despite its commands to keep fighting out of the room. (TV: The Evil of the Daleks)

During the Last Great Time War, the guards possessed a claw-like manipulator arm and some had a more powerful gunstick opposite the standard gunstick. These Gunsticks were said to be disintergration cannons as well as heat sensors. (TV: The Parting of the Ways)

Although he was not the Emperor, Dalek X also had black-domed guards. They were described as having double gunsticks. (PROSE: Prisoner of the Daleks)

Behind the scenes

 * Daleks with black domes are often seen taking part in battles and conflicts depicted in the Dalek Wars section of Doctor Who: Battles in Time magazines, as a result of promotional images of the black-domed Daleks being inserted into the scenery of the battles.
 * According to the non-narrative source REF: Doctor Who: Aliens and Enemies, the Personal Guard also made up the High Council of Daleks, of which the Dalek Supreme was also a member.