Twitter user @Mulsivaas found this image on Waypoint. Putting the pieces together gave him this:
If you go to the Waypoint App on your 360 and press X to open the "Classified" section and X again to Enter Code you can put the above code in and unlock yourself some SPEC Shoulder Armour and 500XP for Halo 4 - Sweet!
UPDATE: That's not all folks! The collective efforts of dozens of people on the Waypoint forums have lead to the discovery of these two codes too:
The code on the left unlocks the SPEC torso armour and 500XP, the one on the right unlocks 5000XP and a concept art gallery viewable on the Waypoint App.
- Cowboy Out.