I think you can use it to fry or sauté anything and it will just give it a different flavor. You could shallow-fry some chicken legs, like a simpler version of confit.
You can saute almost anything in duck fat that you would in butter.
As for duck fat potatoes, rather than pan fry the potatoes in the duck fat, I always liked them better in the oven. Melt a tablespoon or two of the duck fat, toss your potato slices in it to coat, and roast on a baking sheet in a 425F oven until golden brown. Yum!