Skip the meat or pile the veggies on top. Choose among these traditional and nontraditional options: alfalfa sprouts, artichoke hearts, avocado, beans, broccoli, capers, carrots, cauliflower, lettuce, mushrooms, onions, olives, peas, peppers, snow peas, spinach, tomatoes (fresh or sun-dried), and zucchini or other squash.