Deft Strike( Draconomicon, p. 103)
You can place attacks at weak points in your opponent's defenses.
As a standard action, you can attempt to find a weak point in a visible target's armor. This requires a Spot check against a DC equal to your target's Armor Class. If you succeed, your next attack against that target (which must be made no later than your next turn) ignores the target's armor bonus and natural armor bonus to AC (including any enhancement bonuses to armor or natural armor). Other AC bonuses still apply normally.
If you use a ranged weapon to deliver the attack, your opponent must be within 30 feet of you in order for you to benefit from this feat.