Major

Major is a common rank both in the Covenant and the UNSC. "Major" may refer to...

Covenant

 * Major Grunts; red armored Grunts.
 * Major Brutes; armored Brutes of Halo 2.
 * Major Jackals; orange armored Jackals.
 * Major Elites; red armored Elites.

UNSC

 * Major; junior commissioned officer rank of the UNSC Marine Corps.
 * Major General; 3rd highest rank in the UNSC Marine Corps.

Forerunner

 * Sentinel Majors; gold-plated Sentinel constructs with shields.