I'm working on guiding Castille to world domination in Europa Universalis III. An easy choice, but I'm still a beginner.
So far, I've formed Spain, conquered almost the entire Iberian peninsula most of North Africa, Central America, the coast of Brazil, and miscellaneous other small holdings. France got wrecked early on, now Burgandy controls central Europe and Austria eastern, as far as Constantinople. England is still strong, and the Mamluks hold most of the Middle East.
I've also just colonized Hawaii, so in a few decades it'll become a Core Province, and I can begin operations in East Asia.
If you've ever played Civilization and thought "I wish things were more complex" then this game is for you.