True Night's Edge

The True Night's Edge is the third strongest sword in Terraria, beaten only by The Axe and the Terra Blade.

It shoots a large light blade forward on attack. This ability has a short cooldown, so if the sword is being swung rapidly not every swing will fire a glowing sword. If you're standing right next to a solid wall or door which is only one block thick then the fired glowing sword can pass through it. However, it can't pass through the ceiling or floor.