The area around Madison Square Garden is known as a veritable black hole for good lunchtime eats. One exception however, is Pick-a-Pita. Literally located within a warehouse, this teeny shop churns out the best shawarma; and from what I've read, also makes a mean felafel.
Along with their delicious rotessierie dark meat chicken, Pick-a-Pita offers a variety of salads and condiments to make your own sandwich just the way you like it. Toppings include pickled red cabbage slaw, shredded carrot salad, cross-sections of pickles, marinated raw onions, among many others. Everything is extremely fresh and made as you order (sometimes creating a long lunchtime wait).
My personal favorite is the chicken shawarma pita sandwich with hummus, green sauce, harissa, red cabbage slaw, raw onions, extra pickles, with a sprinkle of tahini. This sandwich is a thing of beauty. Click below to see a photo of the shawarma.