I suppose walnuts or almonds would be good but I tend to prefer them with snacks or salads, or occasionally on ice cream. Eggs are under-rated; the latest research says they're not as bad for you as we used to think. And a slice or two of bacon now and then is a part of a balanced diet.
Now if you really want to fill up and have no carbs or sugat, the way to do it all is with eggs and some kind of greens. Cook the greens in the pan with garlic, then scramble the eggs in them, and you have a plate full of deliciousness that's quite healthy and meets your nutritional guidelines.
You can eat healthy food and have it be delicious. You can eat delicious but not-so-healthy foods now and again as well. Moderation in all things!