Solomon Rutzky shows how to use module signing to grant granular permissions to users:
Scenario: We want to allow one or more Users and/or Database Roles to be able to truncate certain Tables, but not all Tables. We certainly do not want to allow anyone the ability to make structural changes to the Table.
Also, it is likely that, over time, at least one more Tables will be added that the User(s) and/or Role(s) should be able to truncate, and less likely, though not impossible, that one or more tables that they should be able to truncate now might be removed.
Truncation is a great example of the kind of right you’d want behind a signed stored procedure, as the level of right necessary to truncate a table is absurd: practically full control of the table. Module signing is something that I wish more DBAs knew and implemented.