I don't know if I've got a favourite per se, but I do have a certain fondness for Konwell (anbennar); They were the first nation I played in a roleplay mp game, and I've definitely got a soft spot for them from that--hard not to after spending so long making up stories and lore for the nation and its rulers.
Dwarves are definitely really fun, and I second that recommendation, along with the gnomes of Nimscodd; artificery is a really fun (and really op) system. Also quite like the Eordand Ruinborn of Pelomar, but I don't have the same kind of connection to any of the other nations I mentioned as I do to Konwell.
I don't play all that much vanilla anymore, so it's kind of hard to have a favourite there. Maybe Savoy.
Very vanilla, but Byzantium - for the flavor and the hard start. For the first few years of the game, it required new strstegies for basically every patch as they adjusted the AI, was a lot of fun to work out how to survive that first war against the Ottomans.
Also had a lot of fun with Manchu way back in the day when it was available at start.
Sadly, I haven't kept up with the game and haven't played in several years - last time I started was when estates were a new feature.
The start was a little tricky, dealing with alliances among the Filipino minors, but overall once I consolidated the archipelago it's been a breeze.
I'd highly recommend it--once you start going into malacca you get near infinite money, and it just becomes a game of eating away at neighbors while you wait for truces. Right now I'm just waiting on gov cap to consolidate Indochina a bit more; maybe take some trade centres from Yue; and then I'll be facing off against Bahmanis, who've allied both Delhi and the Ottomans.
Most satisfying thing in this campaign is beating up colonizers; none of them can stand against my navy, nor do most of them even have enough troops to take me on could they land them.
I might post an update once I get the achievement; haven't played the save much since I took this screenshot, but I'd say I'm on track to finish it off pretty soon game time wise.
Eu4
Hot