What's cool? I guess the answer to that question depends on who is answering it. I think confidence breeds "coolness".
A friend of mine recently showed me an interesting picture blog called the impossible cool. The blog features images of people being...well, you guessed it...COOL! Something more than simply cool, I think the pictures are interesting or "cool" because we know who the people are. These people are hardworking artists, politicians, musicians or actors caught in these candid moments and to see them this way is interesting.
Check it out if you want, here's some of my favorites.
...probably one of the coolest dudes in Cinema, Mastroianni.