Excalibur

The blade throws a wide arc of light that carries well past the metal, so your real reach is much longer than the sprite suggests. In a crowd it caps out quickly, since the arc only bites a few targets per swing. Against one large enemy that extra length is the point: you can stand outside the contact hitbox and still land everything.

Enemies always get pushed away from you, whichever direction the swing goes. That makes retreating while attacking a genuine tactic here, because you keep the distance you are gaining rather than accidentally dragging something along with you. The arc also lights up whatever it passes through, a small thing until you are fighting in an unlit hardmode cavern.

This is a step rather than a destination. It feeds into a later upgrade, so the copy you make after your first mechanical boss keeps its value long after you stop swinging it. The name comes from Arthurian legend, and the game splits the two swords of that story properly: the one pulled from the stone is the Enchanted Sword you dig out of a shrine, not this.