Sniper Kill

From Halopedia, the Halo wiki

Awarded after killing someone with a sniper weapon.

The Sniper Kill Medal is awarded for killing an opponent with the Sniper Rifle or Beam Rifle. It is available in all Multiplayer gametypes where a sniper weapon is available and has a Bungie difficulty rating of 1 (out of 10). It is represented by a six-pointed star with crosshairs. After you kill an opponent with a sniper weapon, a message appears on your screen that says: "You sniped (player)".