I love it when I can pack up a lunch quickly just from the leftovers that I am clearing off the dinner table. It doesn't get much easier than that.
One of our favorite and most simple meals starts with a simple sesame soy noodle dish. You can use any kind of long thin noodle you like. If you have Chinese noodles, or soba, then great. But most of the time I don't - this is a meal I make when I haven't planned ahead, so I haven't bought special noodles for it. Most of the time I make this with just ordinary spaghetti or angel hair pasta. You just cook you noodles like normal, drain, and toss in sesame oil, and then season with soy sauce to taste. It's so simple and so delicious. From there you can add any other shredded veggies or protein you like. I will often put this out as a do it yourself kind of noodle bowl meal - the bowl of seasoned noodles, and small dishes of various veggies and proteins. The noodles are great either hot or cold, so it's the perfect thing for leftovers.
In the lunch the kids have the cold noodles, one has some bites of leftover salmon on top, and one has cut up tomato. They have other veggies on the side, and then a mix of apples, grapes, and blueberries, and then some crackers.