Flash Hider
From the Call of Duty Wiki
Flash Hiders are an equivalent to the suppressor, found in Call of Duty: World At War. They are available for all non-bolt action rifles in the game, excluding the Gewehr 43, which has a Suppressor instead. It is unlocked for a weapon after completing that weapon's Marksman I challenge.
The flash hider greatly reduces muzzle flash, and makes the shooter invisible on radar, meaning it is effective for stealth classes. It does, however reduce range, which can make rifles less effective in sharpshooting (much to the same effect of a suppressor).
Interestingly enough, real flash hiders are actually intended to prevent the weapon's muzzle flash from obscuring the firer's view, and thus affecting their aim, when firing multiple shots. They do not make the flash any less visible to those downrange of the weapon.
[edit] Weapon Combatibility
NOTE: Other weapons use Suppressors to gain the same effect.
