Toughest/Interesting question you've had

As the topic says. Just wondering what the toughest or interesting question you've had so far. Not after an interview review, looking for anecdotal experiences and how you handled the question.

Probably the toughest question i had so far, was from HKUST -
Can't remember the exact question but it goes along the lines of :-

"You're 33 with no financial background so unlikely to be recruited by i-banks, can't speak Mandarin so are competing against people who can for marketing, consulting and management jobs, what type of career opportunities do you think you have in Hong Kong?"

Was a toughie due to its negative slant. I talked about my international experience and the globalisation of companies.

Most Interesting was from NUS -
"Economically, how do you see India and China in 30 years time?"

I focused on China and it's historical GDP in terms of ratio to world GDP. Then brought in the opium wars and cultural revolution to explain the downturn, and how the upturn in GDP should allow it to eventually reach its historical ratio based on the premise of political stability and improved infrastructure and population. I also transferred the last 3 criteria to explain that India also has the same potential.

Probably should have cited post-second world war Japan as an example of a country which developed quickly to become an economic superpower. In fact 19th century Japan is a good example as it was closed off to the world for over 100 hundred years, thereby missing the industrial revolution in the west. After it's ports were re-opened by the Americans for trade, they advanced so quickly to become a military superpower in the region.