Muramasa

The Muramasa is a glowing blue sword that is only found in treasure chests hidden in the Dungeon. Unlike most weapons, you can hold down the left mouse button and it will continuously swing. It may not be the most powerful of weapons, but it can be extremely effective for killing monsters whilst running into them.

The Muramasa has a slightly longer reach than the Phaseblade, and deals 18 damage with a fast attack speed. When used, it will create a small amount of light, useful for unlit caverns or dungeons.

A good tactic is to use the weapon in conjunction with a full set of Shadow Armor and 2 Feral Claws (thereby hitting the speed bonus cap) to give it an incredibly fast swipe speed, allowing you to cut through virtually any enemy with ease.