Shield Sling( Player's Handbook II, p. 82)
[Fighter Bonus Feat, General]
You can hurl your shield as a deadly missile, turning it from a defensive item to a crushing, thrown weapon.
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 Table 7-5, PH 116), 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.
A fighter can select Shield Sling as one of his fighter bonus feats.