I absolutely hate packing lunches but it's not optional in our house. For my school-aged child, I've got her trained to empty her lunch box when she gets home, clean it out, and restock it with a napkin, spoon, and cheese stick. In the morning I put in a container of dried fruit or homemade applesauce, a few pieces of raw veggies, and either a sandwich or a wide-mouth thermos (best invention for packed lunches for school kids ever) with leftovers. DH has a routine of mixing some frozen fruit from our bags we oicked past summer into plain yogurt. Sometimes he stirs in some raw oatmeal. Raw veggies and some type if fruit. A small container of raw almonds. Sandwich or leftovers to heat up at work. Variety seems to be key, but easy is important in our house, too.
I make a lot of hearty homemade bean soups in the winter and those are great as leftovers for lunch.