Slashmaster

From Monkey Island wiki

Slashmaster is a brand of swords. Its slogan is "When you want a sword as sharp as your wit." Similar lines recur throughout the Monkey Island series, usually in reference to Insult Swordfighting.

Guybrush can purchase a Slashmaster from the Storekeeper in Mêlée Town for 100 pieces of eight in the first part of The Secret of Monkey Island. If he does this before securing the Idol of Many Hands, his sword will be taken from him by Sheriff Fester Shinetop who then leaves him to drown. Guybrush can easily escape his doom, and will collect a sword also at the bottom of the harbour if he had one before.

This is the sword with which Guybrush defeats the Sword Master of Mêlée Island, one of the three trials he must complete to become a pirate.