Suicide Grunt

A Kamikaze Grunt is a sort of "berserk" mode for the Unggoy in Halo 3. Occasionally, an Unggoy will prime one Plasma Grenade in each hand and charge towards enemy forces. This mode can be achieved by any Grunt, so it is most likely a parallel to the Brute beserk mode.

Combat
Kamikaze Grunts can be a large threat if not taken care of quickly. To locate and avoid being killed by them it is advisable to take the following three precautions. First, keep an eye out for them - they are usually quite easy to spot since they have a blue glow on each side of them. Second, listen for the Kamikaze Grunts' distinctive screams. This is helpful when you are not using your motion tracker. Finally, do not wait for them to explode on their own. Once the Grunt is killed, the grenades will fall to the ground and detonate, destroying anything in the blast radius of the grenades.

Trivia

 * The name is derived from kamikaze tokubetsu kōgeki tai, Japanese suicide pilots from WWII. The word kamikaze roughly translates as Divine Wind. The name of the suicide attackers was coined after a storm that destroyed a Mongol fleet invading Japan.
 * The Kamikaze Grunt is particularly dangerous if the Halo 3 Catch Skull is turned on, as other Covenant forces will lob grenades at you as the Grunts charge, causing a chain reaction of grenade explosions.