Sonic grenade

Little is known about these grenades, other than that several of these were used by Colonel James Ackerson in testing the MJOLNIR Mark V armor on Reach, hidden amongst the Pillars of Loki and used in conjunction with Napalm Grenades.

Theories

 * The grenade is similar to a Fragmentation Grenade, except that it uses a miniature sonic boom rather than explosives. The grenade is not as effective as a frag, but it is still effective.
 * The grenade is a non-lethal weapon used by Drill Instructors to teach Marines to keep their eyes peeled, hitting them with a loud sound that hurts their ears rather than actually causing them bodily harm. It would be one of the nicer booby traps used by DIs. Though not useable in any of the Halo games, it could possibly be quite effective against Flood infection forms.