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 conjuction 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.