It is now late in the evening as I prepare an answer to your question.  Maybe it’s the fatigue after a day of providing answers or perhaps it’s the nature of the question, but what really grabs me about your question (perhaps in the wrong way) is the word “tools.” 

From a different perspective, I will take the liberty to reshape your question in the form: “If you are only allowed to pick a few organs to retain in the human body, which ones would you select to keep?”  Which organs are the “vital few” and which are among the”trivial many”?  Would you surgically remove those that reside on the bottom of the list?

On a more serious note, here are the thoughts that characterize my thinking:

1) Selecting a tool is much like picking a spouse – both make several assumptions.

2) Black Belts are about ideas, quality engineers are about tools.

3) There are key analytical ideas that every Black Belt should ponder and explore.

4) If tools were the ticket, statisticians would be CEO’s.

5) A simple idea can often negate the need for a tool.

6) The majority of a physician’s curriculum is about knowledge, not scalpels.

In short, it is my belief that Black Belts should be “idea mongers,” not “tool masters.”  We need more creative problem solving and leadership in the world of Six Sigma.  We should be clearly focused on the quality of business and less concerned with being in the business of quality (tool mastery).

Yes, tools are essential – but not above ideas.  Naturally, after spending two decades in the practice of Six Sigma, I do have my favorite tools.  In fact, I emphasize some tools over others, but never to the exclusion of another.  The wide array of intellectual tools exist for a range of valid reasons – every tool has its place.  Of course, the ideal tool list will vary, depending on the application environment and circumstances (engineering, manufacturing, service, transactional, and so on).

As a closing thought, I am gravely concerned over our profession’s preoccupation with tools.  For example, it would appear that our national society of quality is more concerned with certifying the mastery of tools (the base of its existence) as contrasted to the competency of creating solutions (the need of corporations).