I think the most appropriate response to this question is to answer it, but also ask the same thing to them later, which may be revealing, and goes from seemingly rude to perhaps justified.
"Since you asked me about my weaknesses, it seems only fair to ask: What's the worst thing about working here?"
Actually, it's not good advice. It's terrible advice. You'll never get a straight answer out of them. I've tried it myself multiple times and I never got an honest answer. The ACTUAL best way to get the low down on the worst parts of working at a company is to network with former employees and ask them, since they have much less of a reason to fabricate an answer.
I hate this question. I've only heard it from management types, and it irks me because any answer that someone gives is always bullshit. I think its the question that they gauge to see if you can play the political/communication game that big corporations want.
Then again the last time I heard that question I didn't get offered a job. So maybe there's something to hearing it.
I don't think the weakness question has much to do with your actual weaknesses. It a) tests whether a candidate has minimally prepared for the interview (if they stumble over this question, then the answer is "no.") and b) whether they're socially/emotionally sophisticated enough to finesse the question.
Think of it as sort of a game. You may think (as I do) that the game is basically bullshit, but something is in fact being measured by the question, even if it's only how well you play this particular game. And, to be fair, I imagine that if you're good at this game, you'll be good at other useful games (bullshitting, negotiating, etc...)
Yup, it's a good question for bullshitters and negotiators, and there's plenty of demand for both, but for those of us in the substance-based professions, it's a terrible question.
I actually like the question. I answer it honestly, and I always like to get honest answers to it when I interview people. After all, if you lie about your weaknesses, you might also lie about your strengths, and the interviewer might trust you less.
Worse than lying, a huge number of people aren't even aware of their weaknesses, which is probably a big red flag. People shouldn't think they are self-reflective if the only reflection they do is to bask in their own awesomeness.
Being asked to rule yourself out of a job that you are interviewing for (or else deflect the question with some bullshit humblebrag) is far from an ideal gauge of self-awareness.
If you think admitting you are not perfect would "rule you out" of a job it sounds like you haven't really interacted with real humans much (i.e. no sane person thinks that someone talking about something they struggle with when specifically asked is a disqualification). If an employer decides to not offer you a job based on your answer (assuming it isn't something along the lines of "I embezzle massively from every employer"), that is unlikely to be a place you really want to work anyways, in the long run.
The problem is that any answer to the question will hurt you. It's just a question of minimizing the harm. There's also a competitive aspect to it where if you don't lie, someone else will.
"Since you asked me about my weaknesses, it seems only fair to ask: What's the worst thing about working here?"