Fav is definitely Japan
Especially with the new combat, you get three to four combat attacks against a similarly strengthed opponent, but because of the Bushido perk, you keep striking at full strength, and easily defeat your opponent. Its great for a one on one attack, or when you have backup support.
I'm trying to work out a new strategy for the new Gods and Kings. Especially surrounding religion.
Great Scientists seem a waste of time now, and so I go for prophets, or engineers. I get the happiness and production beliefs.
I race to get the national library, build science quickly, then head to the samurai, on harder games, you usually get attacked early, so you just gotta hang in there. I try to get my warriors out there, killing barbarians, collecting city-state influence, and getting them up to 30 exp. I usually level up with a 3 shock : 1 drill ratio. By the time I have samarai, I get them up to blitz, and March.
The only wonders I try to get are Pisa and CN Tower.
My city strategy is maximum population in 3-4 cities, then spam trading posts as I take over civs, starting with the least popular civs. The idea with Japan is to fight and promote early, then build the barracks etc later when its quicker to build.
My last game finished at 1985, with 3500 science, which tells me I didn't get my science up quicker; earlier, so the goal next time is to finish by 1900.
My major problem is unhappiness, gotta work that one out. I think I needed to get the forbidden palace, which I didn't. And I needed to avoid the Honor tree until later, so I could go down the Autocracy tree.
I've finished it easily on King, but want to try it out on a harder level. Overall they are great for warmongering, I'd like to try this out with Germany and Russia.