Grunt

The Grunt/Unggoy (Latin, Monachus frigus, meaning "cold monk" and also monkey in Tagalog) are a small species of servant warriors in the unified races of the Covenant. They are the lowest rank, and are usually used as cannon fodder or hard-labor workers. They are usually mistreated by their higher ranking Elites and Brutes. The Unggoy were one of the first species conquered and absorbed into the Covenant. In appearance, they have a combination of reptilian and mammalian features. They were the third Covenant species to be seen by Humans. They are called Grunts by humans because they are weaker than their Covenant comrades.

Pictures
http://images3.wikia.nocookie.net/halo/images/thumb/b/b5/Grunt-transparent.png/300px-Grunt-transparent.png