Alpheidae/snapping shrimp or sometimes even called pistol shrimp
One of, if not, the loudest animals in the ocean, these shrimp can cock their claw much like the hammer on a gun. When within relatively close proximity (4cm to kill, perhaps slightly larger for a stun effect) these shrimp snap their claws shut creating a sonic shockwave. This sonic shockwave, curiously enough, momentarily reaches the temperature of the surface of the sun, creating light in a process known as sonoluminescence. It is the only animal known using this method to create light, although this light is not visible to the naked eye. Additionally, if the shrimp's dominant arm is compromised, its other arm will grow into a dominant as it regrows a smaller, secondary arm in the compromised arm's spot. Sometimes, though only one has been found as of yet, a temporarily compromised dominant arm will lead to the shrimp having two dominant arms.
A video, though a bit over-dramatic with added gun-cocking effects, is available on just about any video search engine you could look for. Just search pistol shrimp or click
here.
