Sandtrap Hex Egg

On the Halo 3 multiplayer map Sandrap, there is a Hex egg/glitch, nicknamed the Davinci Code egg.

It exists on the huge towers in the distance, and it shoots harmless, tiny lasers at the ground. These lasers are most likely the things that activate the mines when you go too far out.

You can get to it only by getting out of the map via Theater.