I've been carrying a jar of duck fat around for about the past year, and I finally put it to use. I made Kenji Lopez-Alt's Ultra Crispy Roast Potatoes, and they were awesome.
Today for lunch I took the leftovers, added a bit of olive oil, and put them in the toaster oven until they were hot and crispy again. Then I put two sunny side up eggs on top and mixed it all around, so the potatoes were coated in yolk. DAMN it was good. Try it yourself and let me know how it goes!