Generic Japanese restaurants are ubiquitous in Manhattan, so when I discover one that is not generic and has a very fine $10 lunch it's worth mentioning.
Momoya (185 Seventh Avenue, at 21st St., 212-989-4466) has a ten dollar chicken teriyaki lunch that is a steal. It's served with the usual soup or salad, but the soup is a better than average miso soup, and the salad is comprised of greens that are not wilted or brown. The chicken teriyaki itself has crisp skin, moist chicken meat (even the white meat) and a clearly housemade, not excessively sweet, teriyaki sauce. For two bucks more you can get salmon teriyaki instead or for five bucks more you can get rib eye teriyaki.
For a more extensive review of Momoya check out Bruni's NY Times review.