NYC - Not sure how known or unknown, but they're definitely not considered "top" restaurants in the city.
Rocking Horse Cafe Excellent, excellent Mexican restaurant. It's in Chelsea on 8th avenue between 19th/20th.
The Neptune Room - I've mentioned this restaurant before on 2+2...IMO, the best seafood in NYC. On Amsterdam around 84th
Mama's Food Shop - Great home-cooked food. You get a huge meal for very cheap and the sides are awesome (especially mashed potatoes). On 3rd street between A+B
San Loco - Cheap mexican food, but sooo great, especially after a night of drinking. I recommend the Guaco Loco, which is a two-layered taco. It has a hard-shelled inside and has a soft tortilla wrapped around it. It has guacamole smothered in-between layers. There are a few in the city (and I think one in South Beach), but the only one I have ever been to is on Ave. A around 10th street.