Colonial Cross
From Halopedia, the Halo wiki
The UNSC Colonial Cross is a medal awarded to soldiers in the UNSC military. The Colonial Cross is awarded for acts of singular daring and devotion, and is a very high award. It is usually given out in a ceremony recognizing the person who has won the award.
In 2552, Fleet Admiral Sir Terrance Hood held a highly publicized ceremony to award several colonial crosses aboard the Cairo Station.