Michael Condrey has tweeted out an image showing that Sledgehammer Games is currently testing Gun Game mode to be added into Call of Duty: Advanced Warfare MP soon. There’s no ETA for it as of now.
The basic description of Gun Game mode:
All players start the match equipped with the same basic pistol. Each time a player takes out an opponent, they automatically switch to a better weapon. If a player is eliminated by an enemy’s melee attack or dies from self-inflicted explosion, they’re bumped down to a lower tier gun.
Gun Game was actually mentioned in a magazine article, back in November, for Advanced Warfare; however, up until now, the mode was never officially mentioned by Sledgehammer Games.