3rd Battalion 67th Marines
From Halopedia, the Halo wiki
The 3rd Battalion 67th Marines was a UNSC Marine Corps unit mentioned in a draft version of the UNSC Pillar of Autumn page in Halo: Warfleet – An Illustrated Guide to the Spacecraft of Halo. It was stated to be a reinforced battalion of Marines under the command of Colonel Barry Bizzell, which would have accompanied the Spartans and ODSTs on the Pillar of Autumn, presumably as part of Operation: RED FLAG. On Installation 04, the battalion would have been successful in preventing Covenant forces from controlling the Halo ring but would have been overwhelmed and consumed by the Flood soon after.
The 3rd Battalion 67th Marines were presumably intended to occupy the role canonically filled by the 79th Infantry Battalion. The unit was cut from the final release of Halo: Warfleet.