Hamachi-ya is one of the places I like to go to for lunch when I'm in the Pyrmont area. They have a lunch special of the day for $13 which includes a drink, miso soup, the main, often with a sashimi salad as well, and some melon for dessert. Their udon soups and rice with topping bowls are also really tasty.
They're at: Cnr Allen & Harris St, 261 Harris St, Pyrmont.
P: 02 9566 2866, 02 9566 2215. They're open for lunch and dinner.