I've just read a book - rather a good one, I thought initially - that boasts a useless character.
This elderly man appeared at one meal, at which he had to be helped with his food. Occasionally the writer mentioned the number of chairs or people at other meals, which a quick tot-up showed meant he had to be present. Although he was never fed again, not that she mentioned anyway. Once she referred to 'the old man' being helped into another room.
That was it. He had nothing to say, nothing to do, except hang out at the dinner table and not be mentioned.
So why was he there at all? I've thought my way around the symbolic stuff - nothing. Family balance, that kind of stuff - nope, nothing. His presence, as far as I could tell, was completely unnecessary. I wondered if he had had more of a role in an earlier draft, which was then cut, leaving him voiceless, faceless, needing only a chair for the head count.
He was a problem though, when I thought about the book afterwards. This man, who needed help to feed and walk, what was he doing the rest of the time while the family were out and about? Who was looking after him? Rather than just being a presence without consequence, he became a problem in my mind; a loose end that undermined the realism and credibility of the whole story. So what had been rather a good book slid down my mental ratings chart to slumber somewhere at the bottom of the 'well, I won't read that one again, or probably anything else by this author' pile.
If you don't really need a character, if a character has no character, please, please get out your sharp red pen and kill 'em off.