Yeah, from a nutritional stand point it would have to be beans, but there's a price to pay!
I love apples. May not be the best choice, but I wouldn't go crazy if that's all I had to eat.
I would think broccoli. It has a lot of protein, a lot of fibre, loads of vitamins and minerals.
White meat turkey cause it's naturally low in cholesterol and broccoli florets.
Potato. The irish lived off of them for years.