Any of those items dropped from about 16 feet would be hitting me at about 22 MPH (probably less for the feathers), so unless the point of a seed or the corner of a crouton hits me in my eye, none of them would hurt.
Because of their aerodynamic properties, I don’t think feathers or cotton balls could ever reach terminal velocity from any height unless they were propelled by a 120 MPH downdraft. Therefore, I don’t think either of them would hurt regardless of from what height they’re dropped.
If they were dropped in a vacuum and therefore reached terminal velocity, the impact might sting a little, but I doubt that they would cause any injuries.
I’m sure the other items would hurt if they hit me at terminal velocity.