Halo 3 achievements

On a Mythic map, got a Killjoy medal during a ranked or social match.

On a Legendary map, got two Double Kills during a ranked or social match.

Killed 3 enemies within 4 seconds of one another in a ranked free for all playlist.

Destroyed a banshee with the spartan laser or missile pod in a ranked playlist or in campaign.

Claimed Tilt skull.

Killed 10 enemies with headshots in a ranked free for all playlist or in campaign.

Claimed Catch skull.

Claimed Famine skull.

Completed the Campaign on Heroic difficulty.

Claimed Thunderstorm skull.

Claimed Fog skull.

Claimed Mythic skull.