Where is the coolest place to hang out and stay at (hotel) in Boston?

It definitely depends on what you are interested in doing while you are in town, but any hotel in the back bay is probably a good centrally located spot (copley square, newbury street, commonwealth ave, boylston street, etc.)
It's close to the major shopping and dining areas, the park, state house, and not more than a short cab ride away from things like Quincy Market and the North End.