One of the best places I found in Vegas for a traditional East coast style deli experience. They have a large selection of fresh bagels made daily with most flavors and styles you can imagine available. They have a very large dessert case with some very decadent entries. They also have the good old fashioned big old piled with meat deli sandwich available.
The Pizza Bagel is always enormous and tasty, but its a tall order to finish it alone. The deli sandwiches are similar, piled high with your choice of various deli meats. I always liked the cajun spiced turkey breast as well as the classic pastrami, but you really can't go wrong.
If you're from an area that has true delis and are missing it, give The Bagel Cafe a try. Its the closest thing I found to what I love about visiting NYC.