Hijack

The Carjacking (or Highjacker in Halo 3) Medal is awarded for stealing an occupied vehicle from an opponent. It is available in all Multiplayer gametypes where a vehicle is available and has a Bungie difficulty rating of 2 out of 10). It is represented by a cross with a U-turn sign on it. After you steal an occupied vehicle, a message appears on your screen. In Halo 2, that message reads: "You boarded an enemy vehicle", while in Halo 3, it reads: "You highjacked player's name". Also, if you hijack and commandeer a person on the back of a Warthog, you will also get an "Assassination" medal and the person will almost instantly die.