Needs review
Source: Player's Handbook

Description: You are especially good at using a specific weapon

Prerequisites: Base Attack Bonus +1, Weapon Proficiency

Required for: Devastating Critical, Epic Weapon Focus, Gentle Blade of Winter, Greater Weapon Focus, Greater Weapon Specialization, Heaven's Wing, One Leg Stance, One-Strike Blade, Overwhelming Critical, Pole Fighter, Power Critical, Ranged Weapon Mastery, Sanctify Martial Strike, Tail of the Sun, Twisting Blade, Vile Martial Strike, Way of the Crane, Weapon Specialization

Choose one type of weapon, such as greataxe. You can also choose unarmed strike or grapple (or ray, if you are a spellcaster) as your weapon for purposes of this feat. You are especially good at using this weapon. (If you have chosen ray, you are especially good with rays, such as the one produced by the ray of frost spell.)