Hello, how are you?
What is your greatest weakness?
How on earth do you answer a question like that? Well the textbook answer would be to describe how you had a weakness but overcame it. Another way would be the pat "well I work too hard" or make them regret asking and start listing them one by one. I suspect they really don't want to know your weakness much like that time you were asked how you were doing and spent 20 minutes talking about your hay feever and allergies, while they looked increasingly desperate to move away while making the mental note never to ask you anything ever again. It's hard for most people to admit any vulnerability even if they recognise them. My personal wall is quite sturdy but it has its weak points and I'm going to do my best not to tell someone whose going to have a position of authority over me.
So what's the point? You'll have to ask the asker.