From Halopedia, the Halo wiki
Wrecking Crew is a spree medal in Halo: Reach multiplayer, campaign and Firefight. It is awarded for killing fifteen enemies with the Gravity Hammer without dying. It was revealed post-beta along with several new and updated medals in the 05/28/10 Bungie Weekly update.
It is represented by a silver six-pointed star with a Gravity Hammer on a purple background in the center.