Breakfast, bars and baseball.
I have been to 13 ballparks so far. It's my goal to hit them all before we die. I know though that nothing will ever beat Fenway. If you have any love for baseball, you must go here. Even in the cold it was worth it.
Besides that, the clam chowder off Seaport was yummy. Took the train to Cambridge, which was nice (and very clean!). Walked around downtown. Legal Seafood was overrated. Mike's City Diner had breakfast food worth the wait in line. We went to Bukowski's bar and a few others around our hotel. Bukowski's was our favorite. Small, grundgy and people were friendly. Nothing else much stood out to me in Boston but because it holds such a gem of nostalgia in its ballpark it'll always be a favorite.