The opposite of silencers, these things add to the noise and flash of your gun. Works best with ammo loaded with the slowest burning powder you can find. Fit one of these to your .44 snubbie and load with a +P dose of Power Pistol and when used against a late night home intruder, one shot should take out all your windows, knock everyone on their asses, and set fire to everything in the room in which you fire it. The final resting point of the bullet is of no real consequence. In fact, if you should hit the intruder, he'll probably thank you for the quick end to his suffering.
Shown here on an AK platform with a short barrel which should add to the fireworks. Pic of this in action at the link. Spectacular!