MULTIPLAYER SPOILER ALERT. Its not new news, but lots of people dont know.
If you get 25 kills in a row on any streak set (Killstreak kills not included), you get a M.O.A.B. which acts like a tactical nuke, killing everyone on the map and detonating an EMP. Unlike the tactical nuke however, the game still continues, and the team that detonated the M.O.A.B. gets double xp for the remainder of the match. You do not have to unlock this.