One of my new favorites are packets of instant miso soup. It's a delicious and easy way to warm up while cooking a main meal, or to add to anything else you are cooking. Super light weight, and tasty. I also like to bring some dried mushrooms, and add them to quinoa with curry powder. Easy and nutritious meal.
The yellow "safron" (I dont think they are actually safron) plus tuna meal is a classic.