Hash.
OK... so it doesn't sound great. But it has always been one of my favorite meals. And nothing could be simpler... and if you have leftover meat of some kind... even better.
I dice up some potatoes, celery, onions, garlic, herbs, and whatever leftover meat I have... chicken, beef, even fish. I start to sauté the potatoes first, because I want them to stay as crisp as possible later. In another pan, I get the celery and onions going... and when they're almost done, in goes the garlic, and then the herbs. The cooked meat only needs a gentle reheating, so keep it out until the end. When everybody gets together in one pan, add a bit of stock to help them all get along, check for salt, add a ton of pepper and serve. I like to top it with some sour cream, or drained yogurt... but a sunnyside-up egg ain't too shabby!!!