I love remixing leftovers into something new, it definitely can feel more special than just eating the same thing over again... though if it's leftovers of something I really love, I'll eat it right out of the fridge without even dumping it on a plate, I'm not fancy.
If there's leftover rice and it was just a plain side, or even if it had some veg mixed in, it's pretty easy to turn it into a next-day stir-fry, add some eggs and veg and a little hit of sauce. And sometimes I just like to take leftover rice or pasta and turn it into an egg dish, something a little bit like an easy frittata. And I'm always a fan of leftover sandwiches, either after a big holiday meal or if I was lucky enough to have meatloaf.
Stews and casseroles can be good places to dump the contents of your fridge into something new, too. Of course, if what you have leftovers of is stew or casserole, there's not that much to do with it...
Best thing I wasn't the one to make, my aunt turned leftovers into empanadas. Fantastic.