Do you understand what it is that you do well? Do you relate well with your colleagues? Or do you tend to keep to yourself? Are you quick to learn? Or do you take your time to ensure you've absorbed the material? Etc
If you understand what you do well, then you understand other things that you don't do as well. So, in the interview, you refer to those things as your weaknesses. But you follow up quickly by saying how that works well for the company; how you overcome that weakness - e.g. you learn at your own pace, but you overcome that weakness by spending extra time at home focusing on the topic until you're confident that you've mastered it.
I agree that the questions suck, and are manipulated by those who focus on "giving the right answer" instead of knowing what it takes to actually do the job, but such is the state of Human Resources today.