http://www.katzdeli.com/
I've heard many things about this deli and how they are famous for good eats late at night. I tried their traditional pastrami sandwich. It was pretty large and very good. The only thing that I would comment about is that it feels a little overpriced. I went with 6 friends and we spent around $100 bucks easy. Some didn't even order sandwiches. I believe this was about 14 bucks.
Also, definitely try out their deserts. Their chocolate cake was just wonderful. Completely delicious.