I'll admit these sound a little odd, but my kids always enjoy them and they're a fun way to add a little bit of variety into the lunchtime menu rotation.
hot dog roll
It doesn't get much easier than this. Spread some peanut butter on the hot dog roll, peel the banana and put it in the roll. If you want to get really cute, you can put a little strawberry jelly on top of the banana to look like ketchup.
Also just as yummy with almost the same ingredients ~ peanut butter & banana quesadillas! Spread peanut butter on a tortilla, slice bananas on top, then fold in half.