One of the questions amongst the infamous questions James Lipton always asks Hollywood celebs in his bastardization of Proust's Questionnaire is 'What is your favorite word_.' Of course this can only be asked with the overdramatization and English accent in which Lipton excels.
Myself, I love words that roll of the tongue in a fun and pleasing way - the meaning I am less amused by. My favorite words are the ones that are fun to say.
My ideas are a bit along the lines of the mismatched history of 'cellar door' even though cellar door is not my favorite selection of words in English (check out Donnie Darko if you haven't heard of this phenomenon - or check it out if you haven't seen it yet - or just do an internet search and then check out Donnie Darko)
My favorite Swedish word? ömsesidig - pronounced Ohmseseedee (g) (it is my understanding that the final g kind of dances off your tongue at the end)
For me, ömsesidig (despite its confusing spelling) is a word that rolls off the tongue in a most pleasing manner.
It also means something positive - mutual - unlike one of my favorite English words - perturbation which feels almost as uncomfortable as it is.
If you have a favorite word in English or Swedish - what is it? And why?
ETA: For some reason my unedited version was posted here - so I've touched this up. Sorry! Oh, and The Swede says omsesidig starts with an ö.