Face on the moon
From Halopedia, the Halo Wiki
The Face on the Moon is an Easter Egg located in the Halo 3 multiplayer map Standoff. By getting a close look at the moon while in Standoff, you can see a face along the lower-right edge -- the face of Chris Carney, a Bungie employee. This face is quite similar to the ones on the maps Containment and Beaver Creek in Halo 2.
One way to view it is to zoom in on it using a Sniper Rifle. You can also use the Pan Cam in Theater to get very close to the moon.
