Halo 4's various competitive multiplayer modes will feature new ways to slaughter your friends, as well as refreshed versions of old classics, according to a video interview with lead multiplayer designer Brad Welch at Game Informer.
One of the new modes, Regicide, is a free-for-all deathmatch in which one player is the "King," and all other players must attempt to usurp his/her throne. Killing non-King players rewards points as per usual, although not as many as are gained by killing the King, who has a substantial bounty placed upon their heads. Said bounty increases with every successful kill the King accrues during the match, until their demise.
Welch also detailed Halo 4's ranking and unlockable abilities system: Players earn XP as they win, eventually leveling up and being rewarded with Spartan Points, which are in turn spent on new armor abilities. "Forerunner vision," which grants the ability to see through walls, as well as "hologram and active cammo" were named specifically, though we expect that's just the tip of the iceberg.