NaNaNa (Bleach) can use "The Underbelly" to detect the weak points in a individual's Reishi to attack them at those points.
Using his X-Ray Vision, Superman (DC Comics) can scan his opponents for weaknesses, allowing him to perform such feats as precise lobotomies, as he demonstrates on Doomsday...
...and Manchester Black.
Wahl Icht (Fairy Tail) is a Mage that mastered "Weakness" and can extend it to his Machinas which allows him to see the weaknesses of his enemies while creating soldier to counter their magics, while he can alter his own form to overcome his own weaknesses.
Delsin Rowe (Infamous: Second Son) using Laser Insight to detect weak points in his enemies, allowing him to non-lethally subdue them or simply kill them.
Unlike her father Spider-Man, Spider-Girl (Marvel Comics/MC2) can use her spider-sense to detect weaknesses in her opponents and exploit them.
Using her Magic Eye, Mio Sakamoto (Strike Witches) can detect the weak points of Neuroi.