"Tell me about your weaknesses" is indeed one of the classics.
However, it´s somehow a trick question. You want to indeed tell me something that you are working on, but not display a true and important weakness -also, negotiation skills are indeed quite important, I would not point in that direction-.
If you want to deep dive on the topic, the "Integrated FIT guide for MBB" has been recently published in PrepLounge´s shop (https://www.preplounge.com/en/shop/tests-2/integrated-fit-guide-for-mbb-34)
It provides an end-to-end preparation for all three MBB interviews, tackling each firms particularities and combining key concepts review and a hands-on methodology. Following the book, the candidate will prepare his/her stories by practicing with over 50 real questions and leveraging special frameworks and worksheets that guide step-by-step, developed by the author and her experience as a Master in Management professor and coach. Finally, as further guidance, the guide encompasses over 20 examples from real candidates.
Furthermore, you can find 3 free cases in the PrepL case regarding FIT preparation:
Feel free to PM me for disccount codes for the Integrated FIT Guide, since we still have some left from the launch!