I like it on the narrative perspective. How high you roll determines your accuracy to the target location. However, it deals damage still. It can get complicated when the called shot is to a lethal area, but there's ways to narrate it where the player still gets the cool moment.
What are your thoughts on called shots by players?
For example “I am trying to shoot him in the eye” or “I am only attacking their legs so they can’t follow us if we run.”
How do you handle the mechanics?