Unggoy Minor
From Halopedia, the Halo wiki
The Grunt minors are the most common and least experienced rank of Grunt. They are the lowest ranking Grunts and the most numerous enemy you will encounter in the games, save for Flood Infection Forms. They wear bright orange armor.
Combat
Usually found brandishing Plasma Pistols, these Grunts are the most cowardly beings in all of the Covenant ranks and are extremely weak. Killing an Elite overseer or a Major Grunt will usually cause all Minor Grunts in the area to flee.
Minor Grunts are easy to kill no matter what you use, but it is most efficent to either melee them from behind or kill them with a headshot using a Pistol or Battle Rifle.