Ominous

This special ability can only be placed on melee weapons. An ominous weapon trails a shadowy haze behind every stroke, and moans a menacing dirge in battle. An ominous weapon adds its enhancement bonus on Intimidate checks made by the wielder. In addition, when an ominous weapon confirms a critical hit, the target is shaken for 1 minute (DC 13 Will negates); if the weapon's critical multiplier is greater than ×2, this condition lasts 1 additional minute per multiple over ×2. A creature that gains the shaken condition from an ominous weapon cannot gain that condition again from the same weapon for 24 hours.