Possibly the most famous ramen restaurant in Tokyo. Made even more famous by the 'The Mind of a Chef' TV show with David Chang. It's actually in Tokyo station on a stretch known as "Ramen Street". Expect long queues. I arrived around 1.30pm on a weekday and although I was standing on the marker saying 30 minutes, it actually took half that, but I've heard of some people waiting an hour during peak times.
When you're near the front of the queue you will be asked to go inside to the ticket machine to order your food before rejoining the queue. I ordered the special tsukemen ramen which comes with an egg and shredded pork. I loved it and the pork really adds to it.