Sanctify Martial Strike( Book of Exalted Deeds, p. 46)
Sacred power suffuses your attacks with a certain kind of weapon.
Weapon Focus (PH) (with the specified weapon) , CHA 15,
Whenever you wield a specific kind of weapon, it deals 1 extra point of damage to evil creatures, or 1d4 points to evil outsiders and evil undead. In addition, that weapon is considered good-aligned for purposes of overcoming damage reduction.
You can take this feat more than once, selecting a different weapon each time.