Remembering how a gun was the weapon used to murder his parents, Bruce vowed to never use a gun to fight crime. Instead, he created a new type of non-lethal, but still effective, weapon. Thus the "Batarang" was born.
It is a unique throwing weapon designed after the bat motif and is a combination of boomerang and shuriken. Batman carries a variety of batarang types and uses them for different situations.
The curved batarang for disarming criminals and general use.
The straight, throwing knife-esque bladed batarang for cutting and piercing. (There are also "bomb batarang" and scanner versions of these.)
The smaller batarangs shaped like Batman's chest symbol for disabling weapons or throwing a handful at once.