Basic Trope: Someone uses their own death as part of a plot.
The late Mr. Smith's will is filled with secrets he learned over his lifetime, and are told at the reading of the will so that his family starts fighting with one another.
The Big Bad sacrifices himself in a demon-summoning ritual.
The late Mr. Smith's will abounds with wild accusations and reveals terrible secrets, including things he could not possibly have known in life, things which have happened since the drafting of the will, things which have happened since his death, and things the knowledge of which should have prevented his violent end.
Mr. Smith's plot involves time travel, and he has to ensure that he's born in order to succeed.
Mr. Smith's plan is untimely terminated due to the unforseen circunstances surrounding his death.
The Smith family has a history of patriarchs revealing the family's dark and terrible secrets in their wills, but Mr. Smith shocks everyone by simply dividing up his estate and sending his best wishes.
Deconstructed: Mr.Smith reveals the secrets in the will, but everyone comes to hate Mr.Smith for revealing their secrets, uniting in their hatred for him and forgiving each other they bond together and bring down Mr.Smiths good name.
Reconstructed: The departed was tired of life to begin with, and saw more of an opportunity to further his plans from beyond the grave than he could in life.