Oxygen Destroyer

The Oxygen Destroyer was a weapon of mass destruction used to kill Godzilla in his original 1954 attack on tokyo. It was an invention of Dr. Daisuke Serizawa, who feared the power of the weapon and in the end of the film, killed himself when detonating it underwater to kill Godzilla.

The weapon was first demonstrated on a tank of fish, which it instantly reduced to skeletons. When it was used on Godzilla, though, it appeared to destroy the entire creature, bones and all.