Seventh Column

The Seventh Column is a hollow ring with seven rectangular spokes. The one on the top goes into the middle and is not connected to the rest of the ring.

Meaning of the symbol
The Seventh Column represents Bungie's entertaining step to world domination. Each spoke resembles a purpose. They are listed as so:
 * 1) Start independent gaming software company. (Completed)
 * 2) Dominate Mac platform: Launch assault on Windows platform. (Completed)
 * 3) Announce killer gaming title. (Completed)
 * 4) Acquire strangely addictive Chinese food company. (Completed)
 * 5) Recover Ling Ling's head. (Completed)
 * 6) Stage bloody coup of new parent company. (Completed)
 * 7) Take over World. Shoot enemies into sun with giant slingshot. (In progress)

You can find these steps in the extra disk that comes in the Halo 3 Legendary edition.

In Halo
In the Halo universe, the Seventh Column appears to be used by the UNSC in tactical maps to identify friendly units or bases. It appears in the level Crow's Nest and some multiplayer maps in Halo 3, where some of the wall mounted computer monitors have white Seventh Column symbols among the contact icons. Also in Halo 3 the seventh column is on UNSC pilots' helmets.