Not a fancy restaurant, but Mirage has a Carnegie Deli. If it's anything like the world famous Carnegie Deli in New York, it should have some great food.
Link to Mirage Carnegie Deli website.
Some pics from the New York Carnegie. I haven't been to the Vegas one. Here's their famous hot pastrami sandwich.
Big time cheesecake
And of course, no Vegas trip is complete without In N Out Burger.
Animal fries.