Katana, Paragon (3.5e Equipment)
From D&D Wiki
"Katanas are extremely sharp, curved swords first imported from the east. They have become synonymous with warrior culture and a honourable fighting style as well as great skill. Though original smiths were forced to use the only poor quality ore available, they are now able to make use of the best ore around increasing the swords strength and cutting power. Though they are still suited more to cutting down lightly armoured foes due to the blades reliance on slashing over piercing strikes and its inherent brittleness."
Against heavily armoured enemy's the wielder suffers a -1 to hit and if they fail to hit the blade takes 1d2 damage, this ignores hardness. Against targets with light armor or less the katanas critical threat range is increased to 17-20 x3. The blade functions normally against enemy's with medium armor.