Find the Weak Spot, Improved (3.5e Feat)
From D&D Wiki
 Improved Find the Weak Spot [General]
You are able to find the weak spot on non-living entity allowing you to critically damage it.
Prerequisite: Base Attack Bonus +11, Find the Weak Spot
Benefit: May now reduce by 50% the chance of negating a critical hit (treat immunity as 100%). This feat also affect sneak attack and similar abilities.
Normal: You cannot critical hit undead, construct, elemental and others.