I can only comment definitively on the dan pai wudang system, as opposed to fu pai or chou pai, which was passed to me from my teacher via two students of Li Jing Lin.
- I was taught it is the wrist cut.
Wrists are the closest target
Slicing the tendons ends combat
Minimal contact with bone to preserve the edge
In wudang we use the waist and much of the practice, both forms and two-person sets involves drawing cuts, such that many consider these cuts the essence of the art, but these all require being inside the opponent's guard. Even though wudang is also the art of close fighting, the wrist is the first target b/c it can end combat before even getting close.
Major Methods of Wudang Sword confirm this--of the Thirteen Basic Techniques, the majority are wrist cuts, and several others can be used to target the wrist.
Chou (Draw) You draw from left to right to cut the opponent's wrist.
There is upward and downward draw, and it can also be directed at the tendons in the leg.
Dai (Carry) [Vertical] Follow the momentum coming from the opponent to carry their wrist toward you while slicing it. [Horizontal] You carry the sword from right to left, following the momentum of your opponent and cut his or her wrist.
Ti (Lift) The tip of the sword faces downward... against the opponent's wrist. You slice the same way as when lifting an object.
Ge (Parry) ...attack and move the sword upward... in a diagonal direction to cut your opponent's wrist. The turning around Ge is used to evade a close-range attack... You turn your sword around your opponent's sword to cut their wrist.
Ji (Strike) The sword is flat, moving straight forward to strike at the opponent's wrist... use the reverse Ji to strike at an opponent's wrist
Reverse Ji can also be used to cut the ear
Ci (Stab) [the fencer turns] the wrist around doing Ci at the opponent's wrist.
Primary use to stab the abdomen, etc., after a definitive counter, but notable that pricking the wrist is mentioned, because we don't always think of that option.
Dian (Point) Neither the arm or the body moves. You use the strength of the wrist and palm to make the tip of the sword point down to stab at the opponent's wrist.
Beng (making the tip of the sword go upward by pressing the wrist down abruptly) When using regular Beng... the body and arm do not move. Hold the handle of the sword and make the tip come straight up to stab at the opponent's wrist. With Turn-Over Beng, you turn your wrist over to stab at the opponent's wrist from a lower position to a higher position.
"In picture 31 both people are using Turn-Over Beng, trying to continue with the Dian technique to strike at the opponent's wrist."
Jie (Intercept) Flat Jie uses ... while you step forward to intercept the opponent's wrist. In Left Jie you evade the stab [targeting your wrist]. In Right Jie you evage the opponent's attack on your wrist and body. [In] Reverse Jie [you turn your] wrist over to intercept the opponent's wrist from the upper position to the lower position.
Jiao (Stir) ...after circling the sword around the opponent', steps forward using the tip of the sword to stir upward and cut the opponent's wrist.
In the counter, "the wrist should move around the tip of the opponent's sword to avoid being cut."
[The remaining basic techniques are Pi (Split), Ya (Press) & Xi (Slice)]
- 9 out of 13 basic techniques are wrist cuts or can be used as wrist cuts.
These are far from the only techniques, as Li Jing Lin studied many styles of sword in addition to traditional dan pai, and was pre-eminent in dueling.
(Wrist cuts would be more difficult against a basket hilt, and can be avoided by a fencer with sufficient skill, thus one cannot exclusively rely on them.)
My personal experience of wudang free fencing is that it primarily involves wrist cuts, stirring (jiao), and point fighting, and looks more like western historical fencing than people realize, since the art is ultimately governed by the tool and the objective. (In western historical, it has been said that thrust ultimately prevails over cut.) The beautiful drawing cuts we associate with wudang sword and the accompanying waist technique are much more rare.