Divine Shield( Complete Warrior, p. 106)
You can channel energy to make your shield more effective for either offense or defense.
Proficiency with a shield, Turn or rebuke undead ability,
As a standard action, spend one of your turn/ rebuke undead attempts to channel energy into your shield, granting it a bonus equal to your Charisma modifier. This bonus applies to the shield's bonus to Armor Class and lasts for a number of rounds equal to half your character level.