Finnish is my native and as Swedish is also an official language here, all kids need to learn Swedish at school anyway. And when you know Swedish you are basically able to read Norwegian and Danish if you have any natural aptitude for languages.
I used to be rubbish at Swedish, but when the only B in my high-school diploma was in Swedish, I got so pissed off I determined to learn the stupid language once and for all. So, in order to learn Swedish as well as some more English, I went to Scotland to study Scandinavian Studies at Edinburgh uni for 4 years Five birds with one stone!
Modern Icelandic is incredibly similar to Old Norse. I only studied the language of Thor and Loki for 2 years at Uni, basically just reading and translating sagas into English, and was still able to read current Icelandic newspapers. Sort of, anyway.
I like how Icelandic has rejected neologisms unlike most languages, and instead made up words for new phenomena that derive from their heritage. For example, the word for telephone is simi, which means cord/thread, as in a thread between people - just like old landlines used to be! My all-time favourite is their word for computer, which is tölva. It's a portmanteau of tala (number) and völva (prophetess).
"Hang on, I'll just quickly check if there are any new posts on GS on my number prophetess!"