There are so many good ones it's hard to make even a short list. Instead of picking the obvious choices like Vermillion, or Landini Brothers, or the fun choices like O'Connell's and Chadwick's, I want to name a few little ones you might have overlooked. I like Sam Phoa Thai, which is probably the smallest Thai place in Old Town. The food there is great. I also like Parsian, another small but great restaurant. Faccia Luna on the South End is another favorite. Caphe Banh Mi is another tiny stand-out but they've almost gotten too popular.