ability to assign a task to multiple and then for each person to indicate when they are done. the full task is completed when all parties have marked themselves completed.
this way:
the Proj Mgr doesn't need to remember who is done and who isn't
the PM doesn't need to calculate % complete as it could be automated
the PM wont have to create the same task over and over and over again to accommodate multiple people having to do it which overinflates the total tasks and causes mass confusion why the same task is repeated
the task will come off each users MY WORK once they are done so they don't keep seeing the open task and remember they already did it