When  top CEOs and entrepreneurs are asked for their all-time favorite job interview questions, you get a list of entertaining but wildly different answers like:

  • "What would you do in the event of a zombie apocalypse?"
  • "A hammer and a nail cost $1.10, and the hammer costs one dollar more than the nail. How much does the nail cost?"
  • "How old were you when you had your first paying job?"

What can you learn from these suggestions? In short, very little. What companies need and value in employees varies greatly, which means the best questions to get at whether a candidate has the right profile for the job also vary greatly.

But this truth invites one very important question: Are there any job interview questions that absolutely every business owner or hiring manager should ask, no matter the role, industry, or level of experience required? According to several business leaders, the answer is yes.

'Why are you here?'

Any well-structured interview will dig into a candidate's past achievements and failures, hopefully unearthing all the details of their actions and interactions with others. But while most bosses (hopefully!) know how to assess skills in this way, some forget to ask a much more profound question -- not what a candidate can do, but why they want to do it at all.

"The most important question I ask whenever I'm interviewing someone to join the company is 'Why are you here?'" Twitter and Square co-founder Jack Dorsey told Goldman Sachs's 10,000 Small Businesses panel event recently. "If I see passion for our purpose, I know that any skill can be taught," Dorsey explained. "But passion cannot be."

He's not the only one reminding hiring managers not to skip over this essential question. "This is one of the most basic questions to ask but one of the most difficult to answer," Logan Naidu, founder of Dartmouth Partners, writes of the same question in The Guardian newspaper.

"The majority of candidates will turn up well-prepared to answer queries about their professional expertise and relevant experience, but won't have given any time to introspection and why they want to be associated with the organization in question," he continues. If you start the interview off by asking 'Why are you here?' he explains, you invite the candidate to take the lead in demonstrating not only that she's thoroughly familiar with your company and its mission, but that she's also thought through her career trajectory and why she's a good fit for the specific role (and it's a good fit for them).

'Why shouldn't I hire you?'

While hiring managers sometimes skip over the essential 'Why are you here?' question or don't give enough importance to the answer, most at least intend to cover it in some form in the interview. A second ultra-revealing 'why' question is less commonly asked, but equally essential, according to Yashi, CEO and co-founder Jay Gould.

If 'Why are you here?' is the perfect opener, then 'Why shouldn't I hire you?' is the perfect closer, he contends in Fast Company. The former helps you assess passion and fit, while the latter is a measure of character and EQ.

"Everything you need to know can be learned in the moment when you look a candidate in the eye and ask them, 'Why shouldn't I hire you?'" Gould insists. A good answer is less about what the person says than about how they say it -- you're looking for authenticity and humility, not just an attempt to pitch you whatever the candidate thinks you want to hear. Stereotypical "what's your greatest weakness" answers about excessive perfectionism or dedication to the job are a definite negative.

"In looking for people to hire, you look for three qualities: integrity, intelligence, and energy. And if you don't have the first, the other two will kill you," Gould says. "People who are upfront about their shortcomings possess the element of humility that makes them a likeable person you want to work with."