Is there a healthy nut?

All of them. Nuts are an excellent source of protein, fiber, calories (that can be a problem), minerals, vitamins, fats. Each has its own strengths, e.G brazil nuts hi in selenium, almonds-hi in calcium and protein (for a nut), cashews-hi in magnesium, manganese, etc. Calorically dense, so a little can go a long way. Can be helpful in reducing diets, and for most everyone.
YES! Nuts contain healthy fats, and have a lot of nutrition (fiber, good for cholesterol; omega 3 fatty acids, for your heart; l-arginine for arterial strength) in a condensed package. But they are calorie rich, and a high % is fat, so best in moderation. For real benefit, a handful of nuts instead of a junk food snack, all as part of a healthy diet.