Concussion grenade

Concussion grenades are anti-personnel devices that are designed to damage their targets with explosive power all alone. Compared to fragmentation grenades, the explosive filler is usually of a greater weight and volume. The case is far thinner and is designed to fragment as little as possible. The shock wave overpressure produced by this grenade when used in enclosed areas is greater than that produced by the fragmentation grenade. Therefore, it is especially effective in enclosed areas. Copy and pasted from wikipedia!!! http://en.wikipedia.org/wiki/Concussion_grenade#Concussion_grenades

They were used by Team Foxtrot in Operation TORPEDO to disorient a squad of six Elites so they could destroy a Covenant factory there.