Meats - you have options of bacon, breakfast sausage, ham, chicken, and turkey. This is a great breakfast dish to use up leftover meats. Cheeses - cheddars will give you great flavor, especially sharp cheddar. You can also use shredded Mexican cheese mix, Colby-Jack, or Mozzarella. Vegetables - think hardier veggies like onions, bell peppers, mushrooms, zucchini, chili peppers, or corn. Beans - use refried or black beans if you'd like.