I really like Hyde and Hot Shop for their tasting menus. Obviously a bit of a luxury since it comes out to around 1k per person, but if you're looking for something that tastes so good you can't stop smiling - highly recommend.

Szhechuan Chengdu as others have said for Chinese - but be sure to book a table, they're always full.

Izakaya is the Japanese basement bar with snacks, real good but gets real expensive if you want to actually feel full.

Las cazuelas sabor a Mexico is pretty basic but pretty good texmex, doesn't try to be something it's not and the prices are decent.

Registan is Uzbek food, if you want to try plov and manty give it a go - it's not mind blowing on a global scale but you don't have any other Central Asian options in Oslo (correct me if I'm wrong). On a similar note, I wish there were more options from the caucasus as well, Georgian and Armenian food is so dreamy, I really miss it.