I think the word merits a deeper look. As a bilingual (or semi-trilingual if you consider my rudimentary Finnish skills), the word does not have any every-day equivalent in my native language Turkish. I happen to know a somewhat impressive repertoire of vocabulary in languages I don't speak fluently, and to this extent, I am not aware of an equivalent of 'cool' in any other language, too, as a word that has such variable meaning that it is practically meaningless to an outsider.
Now that I'm studying in Canada this outsider-ness is especially apparent to me; the usage of the word 'cool' I have witnessed so far led me to think that making a list of what can be considered 'cool' would be—under the light of my thoughts above—a list of what is considered 'cool' would be a list of the 'apex' of what the mainstream/popular cultural denotes as desirable.
I came up with the following list with a few people.
•join a pseudo-gang
•wear leather stuff
•be cultured but do not be too cultured as to look like a 'dork'
•be able to cook good food
•play bass guitar
•wear fashionably unfashionable clothes
•lean against walls
•name your bruises (e.g. Bruce Willis, Bruce Lee, etc.)
•get people come to you
•be lighthearted but also sufficiently serious
•have a diary
•discretely do stuff that people don't know about (but don't do that stuff too much)
•near death experience
•one-time psychedelic experience
•being wittily facetious
•swearing in foreign languages
•staying up late (but not too late)
•skating & the like
•making silly lists
•having online friends