There are no "special" food. It all boils down to the calorie intake. You need to consume more calories than you need. How much calories you need depends on factors like body type and metabolism. Here are some food ideas:
Proteins:
Boneless, Skinless Chicken Breast
Tuna (water packed)
Fish (salmon, sea bass, halibut)
Shrimp
Extra Lean Ground Beef or Ground Round (92-96%)
Protein Powder
Egg Whites or Eggs
Rib Eye Steaks
Top Round Steaks or Roast (aka Stew Meat, London Broil, Stir Fry)
Top Sirloin (aka Sirloin Top Butt)
Beef Tenderloin (aka Filet, Filet Mignon)
Top Loin (NY Strip Steak)
Flank Steak (Sir Fry, Fajita)
Eye of Round (Cube Meat, Stew Meat, Bottom Round, 96% Lean Ground Round)
Ground turkey, Turkey Breast Slices or cutlets (fresh meat, not deli cuts)
Complex Carbs:
Oatmeal (Old Fashioned or Quick Oats)
Sweet Potatoes (Yams)
Beans (pinto, black, kidney)
Oat Bran Cereal
Brown Rice
Farina (Cream of Wheat)
Multigrain Hot Cereal
Pasta
Rice (white, jasmine, basmati, Arborio, wild)
Potatoes (red, baking, new)
Fibrous Carbs:
Green Leafy Lettuce (Green Leaf, Red, Leaf, Romaine)
Broccoli
Asparagus
String Beans
Spinach
Bell Peppers
Brussels Sprouts
Cauliflower
Celery
Other Produce & Fruits:
Cucumber
Green or Red Pepper
Onions
Garlic
Tomatoes
Zucchini
Fruit (if acceptable on diet): bananas, apples, grapefruit, peaches, strawberries, blueberries, raspberries
Lemons or Limes
Healthy Fats:
Natural Style Peanut Butter or Almond Butter
Olive Oil, Safflower Oil, Almond Oil, Flaxseed Oil
Nuts (peanuts, almonds, walnut)
Nuts and seeds (butternuts, flaxseeds, walnuts, soybeans) - Omega-3
Fatty coldwater fish (mackerel, salmon, bluefish, mullet, sablefish) - EPA and DHA
More fish (menhaden, anchovy, herring, lake trout, sardines, tuna) - EPA and DHA
Olive, Canola, and Peanut - Monounsaturated Oils
Safflower, Sunflower, Corn, Soybean, and Cottonseed - Polyunsaturated Oils
Leafy veggies, seeds, nuts, grains - Omega-6
Veggie oils (Safflower, Sunflower, Corn, Soybean, and Cottonseed), and poultry fat - Omega-6
Oils (canola, flaxseed, soybean, walnut, wheat germ; canola or soybean oil) - Omega-3
Dairy & Eggs:
Low-fat cottage cheese
Eggs
Low or Non-Fat Milk