Hero Sword

 was an unused gun that was updated in the Farewell to Arms update to an unused active item. Using it as an active item sticks the sword out in the direction of your crosshair, doing 100 damage every frame for a second. Despite this, its recharge is less than a second.

Trivia

 * It is unknown why this gun was cut.
 * The tooltip references the wordplay of Gungeon, but using Sword instead.
 * The weapon bears a strong resemblance to the White Sword from the original Legend of Zelda.
 * With this in mind, it is possible this weapon was an earlier edition of The Bullet's signature weapon, Blasphemy.
 * Its behavior as an item bears some resemblance to Mom's Knife in The Binding of Isaac.