You are skilled in lining up accurate, deadly shots with your crossbow. Perhaps you add custom-made sights to your weapon, or you have learned to maximize the stability and precision the weapon offers.
Weapon Focus (PH) (Hand, heavy, or light crossbow) , Weapon Proficiency with Hand, heavy, or light crossbow, Base attack bonus +1,
When using a crossbow for which you have the Weapon Focus feat, you gain a bonus on damage rolls equal to 1/2 your Dexterity bonus. If you have the skirmish or sneak attack ability, the maximum range at which you can make such attacks increases to 60 feet when you are using a crossbow for which you have the Weapon Focus feat.
A fighter can select Crossbow Sniper as one of his fighter bonus feats.