Kig-Yar Major

Jackal Major is an elevated rank for more experienced Jackals of the Covenant. They are characterized by their orange shields, and usually wear armor that is beige or brown in color, though this is not always the case. They are seen commanding Jackal Minors or Grunts in combat. Their shields become gradually red as they weaken in strength.

In Halo 3, their shields appear to be light purple.

Combat
Jackal Majors almost always wield Plasma Pistols which they are fond of overcharging. Be very careful when attacking them from the front. These Jackals are trickier than their less experienced counterparts. They are better at blocking themselves with their shields, and can usually roll out of the way of a Frag Grenade. The best way to kill them is to Melee them, or use a M6C Magnum and land a headshot for an instant kill. This will also work with the Covenant Carbine or the BR55 Battle Rifle as well, or alternatively using a Sniper Rifle to kill them from afar.

Like Minor Jackals, Major Jackals are not tough and should be taken down at your own pace, They are so rarely found alone though, often lead by Lances of Grunts...

Appearances
They appear in almost every level in Halo: Combat Evolved, Halo 2 and Halo 3, with a few exceptions, such as The Library in Halo: CE or The Oracle (Level) in Halo 2.

Halo 3
Though they are not listed in the Bungie.net stats, Jackal Majors are likely in Halo 3 as the violet shield bearing Jackals. On Legendary, these are more common then their blue shielded counterparts, and with Thunderstorm active violet shielded Jackals are the only shield color that appear.

Trivia

 * In Halo: Combat Evolved for the pc, it looks like the textures, coloring, and all out graphics were never completed or they didn't transfer from the xbox to the pc very well. So Jackal Minors and Jackal majors have the same shield color (turquois). In the xbox version, the Jackal majors have light orange shields while the minors have dark blue shields.