I don't like to waste food so there are many re-uses other than simply re-heating and serving leftovers. Here is a sample of some that come along and what I like to do with them.
Not that we'll change to this a food site but let's see where food does get us.
Leftover -> Re-use
Baked potato -> home fries
Ham bone -> pea soup
old bananas -> banana bread
old bread -> bread pudding
ham slices -> ham hash or ham omelets (or both)
If you have different uses or other suggestions, please share.