Mimetic (3.5e Equipment)
From D&D Wiki
Mimetic: The wielder of a mimetic weapon may will the weapon to take the shape of any type of weapon he desires. When transmuting the weapon, he may bestow the weapon with any appearance he desires. When changing the mimetic weapon into a different type of weapon, it gains all the properties of that weapon, including base damage, threat range and critical multiplier. The mimetic enhancement only allows a weapon to change in other weapons intended for creatures with similar size category as the original weapon. A mimetic weapon cannot change into any sort of ammunition or weapons treated as ammunition.