Down the hill off Union Square are Cafe de la Presse and Scala Bistro, If you take the California Street Cable Car down the Ferry Bldg MarketBar has started doing weekday breakfast and there is also Boulette's Larder inside. Coffee and baked goods at the Little Cafe at California and Powell (name escapes me) - Mom lives a block away and swears by the banana bread. I enjoy the casual bar food at the Big Four at the Huntington - never tried breakfast but you might look at the menu. Enjoy.
1075 California Street, San Francisco, CA 94108
You will get more responses if you can be a bit more specific i.e, what do you consider "unique', what kind of cuisine's do you like or dislike, what do you consider "serious cash", etc. To get things started, though, I'll throw in Aziza as being somewhat unique and very good, La Mar or Mochica for Peruvian, Tadich Grill just because it's very old San Francisco. Those are all for dinner. i've only been to Canteen for dinner but it gets raves or its brunch.
240 California St, San Francisco, CA 94111
937 Harrison Street, San Francisco, CA 94107