You can hurl your shield as a deadly missile, turning it from a defensive item to a crushing, thrown weapon.
Prerequisites: Shield Proficiency, Improved Shield Bash, Shield Specialization, base attack bonus +9.
Benefit: You can wield your light shield or heavy shield as a thrown weapon with a range increment of 20 feet. The shield deals damage as normal for its size (see Martial Weapons), and you gain your Strength bonus on damage as normal for a thrown weapon. In addition, you can make a ranged touch attack to initiate a trip attempt. Your target resists the trip attempt as normal. You lose your size bonus (though not a size penalty) on your Strength check. If your foe’s check succeeds, he cannot attempt to trip you.
You cannot throw a tower shield. You can throw a buckler, but it does no damage, and you cannot use it to trip an opponent.
Special: A fighter can select Shield Sling as one of his fighter bonus feats.
Source: Player’s Handbook II, page 82.