I believe the following set of abilities are very central to successfully perform the tasks of a management consultant at MBB firms:
1. Curiosity: Intrinsic drive to get to know root causes of visible effects and/or problems. The urge to understand the "Why?" and "How?" on top of the "What?"
2. Ability to listen and absorb: This is absolutely central! In daily interaction with clients, you should be listening at least 80% of the time! Being able to absorb and connect information from multiple sources and layers across the client organization is one of the essential success drivers for almost any consulting engagement.
3. Ability to analyze and synthesize: Disaggregating problems into their sub-components, addressing the corresponding sub-issues, and then integrating the insights into the big picture and larger frame is the bread and butter for a consultant. In short: rigorous problem solving skills.
4. Mental flexibility: Capability to quickly adapt to shifting priorities, swiftly re-focus on newly generated insights or refuted hypotheses. This goes hand in hand with a structured way of thinking about practically ANYTHING. Why? Well, in its operational core, strategy consulting is amongst the most chaotic and unstructured activities in the professional world. This is why the individual consultants need to be utterly structured in their thinking, hence leading to this flexibility and confidence that they can logically disaggregate practically ANY problem thrown their way.
All of these abilities will have a immense positive impact on almost any dimension of the consulting job: be it problem solving and insights generation, connecting and working with clients, codifying new IP for the firm, coaching younger colleagues, etc.