Following the success of Black Ops' zombie mode Perk-a-Colas, Treyarch have decided to add Mule Kick to all maps.
Treyarch is adding the perk after "receiving positive reports" from players who played Rezurrection's new map Moon, where players enjoyed Mule Kick, a perk which allows players to carry three weapons at once. Obviously, these changes will only apply to Call of Duty: Black Ops and will affect all platforms.
After good reception, every zombies map (excluding Dead Ops Arcade) is to receive the Mule Kick machine.
UPDATE - Sorry I got the wording confused, apparently ""...Mule Kick is available for purchase in every Zombies map, in addition to the other Perk-A-Colas..." doesn't mean the other DLC Perk-a-Colas. Blame Treyarch ;)