Major

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

In the Covenant
 * Major Grunts, the red armored Grunts.
 * Major Brutes, the armored Brutes of Halo 2.
 * Major Jackals, the orange armored Jackals.
 * Major Elites, the red armored Elites.

In the UNSC
 * Major (UNSC), the rank of a Marine officer.

In the Forerunner
 * Sentinel Majors, the gold-plated Sentinel constructs.