The squire who brought Trebuchet’s Sword to the Fisher King, along with the message that the Fisher King’s niece had sent it and that she would be greatly pleased if it were passed along to a suitable champion who would use it well, strikes me as a responsible enough character to merit individual inclusion here.
In a sense, his errand can be said to herald the Grail procession. I am not sure whose squire he was, the Fisher King’s or the niece’s, but he was quite well informed.