The basics:
Eggs
Tuna
Chicken Breast
Oatmeal
Milk
Potatoes
Broccoli
Lettuce
My favorite food for gaining muscle are chicken cutlets fried in an egg wash. They're always great even when I'm tired of eggs alone or chicken alone.
Another staple of mine is a big tuna, hard boiled eggs, and lettuce salad. I make an italian dressing out of garlic, balsamic vinegar, and olive oil for that salad. Gives me plenty of fiber, EFA's, and protein, and it's just a salad! I eat it with lunch and dinner. You can throw in different veggies each day for variety (carrots, tomatoes, zucchini, etc)