I got the least-guessed answer pretty easily because I learned it as the "Yukon Territory" instead of just the "Yukon". Imagine my surprise when I look it up and find out the name changed before I was even born!
Pretty surprising that BC isn't at the top of this list, easily the most intuitive postal code given it's exactly the same as what the province is called most of the time.
I managed to get the least-guessed answer when I thought about the fact that it is a territory, not a province.