Double Kill

Were you looking for the Halo 2 Vista achievement of the same name? The Double Kill Medal is awarded for killing two opponents within four seconds of each other in standard Multiplayer games and within less time in Campaign and Firefight modes. It is available in all multiplayer gametypes and has a Bungie difficulty rating of 5 out of 10.

Description
It is represented by a brass and yellow circle with two blue stars in the center of the circle. When someone attains and achieves this medal, the announcer will shout "Double Kill!" to the player as the "Double Kill!" medal appears in their HUD. In Halo: Combat Evolved due to a lack of visual medals however, the words "Double Kill!" will appear in the upper right corner of the screen. It is the most frequently earned multi-kill medal.

Trivia

 * After the Title Update 2 for Halo 3, getting two of these in one game on a Legendary Map would award the player with the achievement Double Double.