The Silver Sword is among the better buyable weapons, boasting decent +ATK and good scaling for a middling price. Although not a must, it is well worth the money if you haven't chanced across a Dark Sword or have somehow accrued enough gold to buy a Knight Sword. It is also dropped by an enemy, but that is so far into the game that it will probably have been bought before that.
In-game stats Edit
Category, ID: 0,18
Drops from: Blood Paladin @ LV 8370, Haunted Castle (to the left)