Depends if you're talking health-wise or just what our favourite breakfast is. Protein rich breakfasts will fill you up for the day, and release energy slowly, which is a good excuse to indulge in a big breakfast with eggs, bacons, mushrooms, and beans. Big breakfasts do tend to be very fatty and calorific though.
Muesli is a good choice. It is full of whole grain, releases energy slowly, and is a lot less fatty.
I don't eat breakfast any more, but when I did my two favourites were a bacon sarnie or tinned pineapple.