Sunflowers are pretty darn hardy, they get big, impressively so. Then you can either harvest and roast or leave them out for the birds all winter. Second on my list is pumpkins or any winter squash, they need lots of space though and can be devastated by bugs early, a real dissapointment. Avoid sweet corn needs lots of room for the yield, green beans aren't too bad either, the seeds are big and they won't be easily dropped.