Flashbang grenade

A Flashbang Grenade (also considered a stun grenade) is a special type of grenade used by the UNSC. Unlike Fragmentation Grenades, these grenades are not intended for lethal use. Flashbangs use chemical reactions to produce an extremely bright flash of light and a very loud concussion blast when deployed, stunning targets, but doing very little physical damage to them. The primary purpose of a stun grenade is to temporarily blind and deafen the enemy. If the victim directly observes the flash, a still frame of what is observed by the victim will be seen for up to ten seconds, at which point their eyes will have returned to their unstimulated state.

Due to widespread usage within 21st Century armed forces, it has likely been used since the UNSC's conception, though the earliest recorded use of it was 2552. Flashbang and stun grenade's use in combat scenarios has not be overlooked, serving to confuse, disorient, or momentarily distract a potential threat for five to ten seconds.

Triva

 * Halo 3 possesses a piece of equipment serving a similar function as a Flashbang, the Flare, which is used to blind all nearby players, though it lacks the deafening effect of a flashbang. It does, however, have a noise that can drown out certain other sounds.
 * Within the UNSC, along with some 21st century armed forces, they appear as hexagonal tubes.
 * In modern days, flashbang grenades are used in special operations, counter-terrorist forces, specialists to avoid casualties on both sides and provide quick escapes and diversions.
 * Some speculate that a flashbang grenade was used by Marines during the Halo 2 demo.
 * Hellbringer troops will be able to use them in Halo Wars.