We're TF(ish) and low carbish at the moment. Breakfast usually isn't dinner food, but breakfast and lunch are pretty interchangeable. In fact, we get up abominably late, so they're often one and the same.

Filling, though!
Quite often it's fried eggs and fried/wilted pak choy; occasionally we have sardines on homemade sourdough bread. When we're feeling prosperous we do bacon; on rare occasions, bacon and maple syrup and cream on pancakes. DH likes porridge in theory, but according to TF principles it has to be soaked, which we never remember to do, and he ends up eating a miniscule amount anyway. DD and I don't like it much. Probably the most specifically breakfasty food we have is yoghurt with honey and cream, but that's mostly DD, not the big people.
I should probably expand my breakfast repertoire a bit, DH says he's getting sick of eggs (heresy!). We do smoothies in the summer, but it's hard to get excited about them in winter...