Green smoothies
Home made easi yo yogurt, Greek or stevia sweetened,
Scrambled egg with mattersons smoked sausage
Sliced ham and cheese (the quickest and easiest ever! Don't even need a plate)
Low carb cake (basically almond flour, egg, apple, cinnamon and xylitol)
Fruit and yoghurt
Yoghurt and low carb muesli
Coffee with double cream
Bullet proof coffee (google it. Yum)
Omelette
Spanish omelette
Cheese
Ham spread with Philadelphia and rolled into a tube (very portable)
Get Up And Go by Patrick Holford
Almased
Home made hot chocolate (cocoa powder, double cream, xylitol)
Grilled open mushrooms with cheese (or ham, or mattersons sausage)
Smoked salmon (without bagel)
Bacon and egg
Sausages
Fried breakfast (minus toast, hash browns and fried bread)
Livlife bread as toast
Low carb biscuits (made with almond flour not wheat flour)
Low carb pancakes (made with coconut flour)
And, as Beachbag says, anything you eat at other meals.
Admittedly, most of these are only practical at weekends when you have more time.
On work days, for me, it is usually a green smoothie, or yoghurt and fruit, or bullet proof coffee, but I am about to make some low carb butter biscuits. Will see how they go...