I often hear peanut butter recommended as a protein source. Yes, it does have protein. But, ignoring the fact that it's not even a complete protein, it is so high in fat that you need to eat 190 calories of it just for a measly 8 grams of protein as shown by this graphic posted by @samgbbg. Eggs are similar but not as extreme. Just because a food has protein doesn't mean it should be viewed only as a protein source. Peanut butter should be viewed as a fat source that has protein. Eggs should be viewed as an equal source of protein and fat. There is nothing wrong with either of these foods but if you're eating either peanut butter or eggs strictly for protein, you're going to be eating a large amount of calories with it if you're not factoring in the other macronutrients. If you are looking for a food that is only protein, I'd recommend chicken, turkey, fish, egg whites or whey protein.