Italian Beef is kind of a Chicago regional dish, though I'm sure it's made it beyond our wonderful city.
Requirements for this are the following:
white onions
peppercinis
garlic
oregano
Beyond that, the season is really up to you. I use salt of course, and cracked pepper, and usually some basil and thyme.
Italian beef usually uses the cheaper, tougher cuts, because that connective tissue will break down over the long cooking time. For additional flavor, you can use beef broth instead of just water.