I think another thing not mentioned here is tomatoes. In my experience they are great because you can get pretty high yields off only a couple of plants. And best yet, because of their acidity, they can easily be canned and stored for very long periods of time. My favorite are San Marzano but Roma are very similar and can net absolutely huge yields, and are pretty hardy. Also packed full of nutrients, and in hard times this could be the difference between vitamin deficiency and peak performance.
Biggest issue I've run into with tomatoes are various blights. Last year was really bad for Septoria (lots of rain and not enough sun). Also very important to track where you grow them. Crop rotation is key and tomatoes have a tendency to leach certain key minerals from the soil, so they absolutely must be rotated. Most fungal pathogens for tomatoes come from the soil, as well as improper drying of the leaves (from lack of sun). Best means to avoid blights are 1) having some sort of mesh over the soil 2) avoid water the leaves directly 3) watering earlier in the day 4) spot infection early and remove those parts of the plant that are sick.