Kyushu in Neutral Bay - Affordable, fresh food and delicious. They're always busy so book ahead. They have the best teriyaki squid.
Tsukasa in Surry Hills
Juju's in Darlinghurst - Japanese Saloon-like atmosphere where you can hit the piss, eat good food then sing some karaoke!
Kai on King - King st Newtown. One of the best sushi bars I've been too in Sydney. Always fresh, excellent prices. Plus they had a stunning waitress there last yr