Deft Strike

 
Prerequisite(s): Int 13+, Sneak Attack, Spot 10+ ranks, Combat Expertise
 
Benefit: 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 AC. If you succeed, your next attack against that target (which must be made within one round) ignores the target’s armor bonus and natural armor bonus to AC (Including enhancements to these). If you use a ranged weapon, you must be within 30’ of the target.
 
Source: Complete Adventurer, Draconomicon