Country Club USA, Chelmsford, MA
I second that, I did not often go to that room, but when they were going and pool was also going, the had some nice tournaments there.
Country Club was the place I first saw pros in person, including a teenage Alex P that was drawing a crowd even then.
Another one in Boston area that was a great room was Brighton Billiards. Basement room with 8 pristine setup GC tables, tight space, crowded, waiting lists, smoked in, but always enjoyed going there. It would probably have to be a tie for me between Brighton and CC if I could only see one open, but it has to be with the provision that the rooms were like they were in their prime for any of them. I don't want to see some run-down place with 3 players in it and 14 kids spilling their beer on the tables listening to rap about doing chicks and buying cars.
A lot of rooms closed in the Boston, central MA area that I miss, Mr Billiards in Framingham where I learned to play, GeeCues in Marlborough, Boston Billiards (oddly enough for a chain this was one of the bigger action rooms in the area). About 3-4 more rooms closed that I visited for tournaments.