My son takes tons of different lunches to school, but his favorite is still PB&J. We mostly had him take capri suns or juice boxes to school.
IDEAS: Tuna sandwichs, chicken salad sandwich, fried chicken, ham wraps, PB&J wraps w/ apple slices in it, mac N cheese, lunchables, BLT's, cold cut sandwichs, sausage w/ beans & rice, spagetti O's, hot dogs, leftover pizza, & chk nuggets. I am sure there is tons more, but this is all I could think of right now. We experimented a lot last year.
Stuff to help:
if your child likes apple slices w/ lunch, go ahead and put them in a ziploc baggie, but suck the air out with a straw, that way the apples do not get nearly as brown.
If you are sending like a hot dog with a bun, toast the bun real good (so it does not get soggy) and wrap in tin foil, keep it seperate from rest of lunch. Also keep packets of condiments from restaurants, they work real good to just throw in the lunch bag.
If you are concerned that his/her lunch should stay cold, make a ice pack the kids can throw away. Take a few ice cubes and wrap in paper towel then double bag in ziploc bags.
For the most part, everything in my son's lunch he could throw away because he had a hard time remembering. Hope this helps.