Masterkey

For the similar attachment found in Modern Warfare 2 see Shotgun (Attachment)

The Masterkey shotgun is an available attachment for most assault rifles in Call of Duty: Black Ops.

Campaign
The Masterkey is a rare attachment found in the singleplayer campaign. It can be found on the level SOG, mounted to the player's starting M16. In the same level, the Marines will occasionally drop an M14 with this attachment when killed. It is also found on the 2nd part of Rebirth, on the Enfield.

Multiplayer
The Masterkey shotgun is available to the player for. It is compatible with most assault rifles with the exception of the G11. It is essentially a mounted Stakeout, as both shotguns have the same rate of fire, magazine capacity, and range stats, however the Masterkey deals 30-10 and the Stakeout deals 40-10, also the Masterkey has a smaller spread than the Stakeout. Unlike the two other underbarrel attachments, the Scavenger perk will occasionally restore an amount of shells for the Masterkey, although it is not a guarantee.

Zombies
It is available on the Pack-a-Punch version of the AUG, and seems to do relatively high damage, even comparing to the Stakeout. However, it starts to lose its ability to kill in one hit about round 17. It will reload 2 shells at a time, just like the Raid.

Trivia

 * The term "Masterkey" originated from the ability for a shotgun to open doors (aiming for the locks and hinges), which was developed into an underbarrel shotgun called "Masterkey".
 * The Masterkey is one of the rarest attachments used in Black Ops multiplayer. Still, it is seen more than in Modern Warfare 2 due to the fact that shotguns were removed as secondary weapons.
 * As with all underbarrel attachments, the Masterkey cannot be used with another attachment (using Warlord).
 * When wielding a Masterkey, a player will grasp the pump with the left hand, but the trigger is not touched.