If you were given the power to make one significant change, in the world, your country, in your life, or in someone elses life, what would you choose?

Eradicate cancer. Nasty stuff.

Make college free. Instead of spending untold treasure on wars and propping up ignorance, dedicate those sums to prioritizing superior education and making it available to everyone. Better understanding is a boon to our species.  Cure ignorance, reduce the causes of hate. 

Abolish cruelty .. Towards all humans and animals

Having the world be more patient, kind, compassionte and tolerant of each other.

Free education, especially college. It'd be much, much easier on my financial status.

Everyone in my hypothetical country would have a minimum IQ of 120 and IQ's of 150 would be very common. We would have an unfair advantage over all of our neighboring countries in every way.