Maishin is worth knowing about for their serious sake selection and their Sunday hours, a day of the week when many sake specialists are taking a holiday. You'll find lots of limited-edition seasonal specials from small breweries, and the staff are ready to offer advice (in Japanese), or you can peruse the menu (also in Japanese).
The food here is decent, but it definitely plays a supporting role for the sake. The steak with foie gras, however, is quite good, and the sashimi is generally reliable. There's an amusing half-height door that you have to climb through to enter; if it's not as amusing when it's time to leave you can ask them nicely to open it all the way. Budget around Y4000-6500 for ample food and drink.
This book will introduce you to more than twenty of Japan's favorite specialty foods that are less well known abroad, along with a guide to the best places in Tokyo to try them and expert tips on what to order. From Bento.com.