Sushi Yasuda [204 E. 43th St. (bet. 2nd and 3rd Aves.) 212-972-1001]
Treat yourself to a uniquely fantastic sushi dinner here and you will not be disappointed (and if your wonderful girlfriend takes you, things will taste even better...). The fish is fresher and more diverse than at any other sushi restaurant this side of Tokyo. Make sure to choose your fish wisely and look for the freshest fish of the day (they give you a menu for this). I also recommend trying some of the fish that you don't normally see, such as Tasmanian Trout, Fluke, or White King Salmon. If you can afford it, certainly try the Omakase. The decor is spare, but classy.