Cold eggplant is ahead in the poll, followed closely by marmite, and I have to say: I do not understand you people. What could be more unnatural to put on toast than guacamole! I mean, all right, marmite is a valid choice, since it's bad no matter what you put it on, but I would far rather eat cold eggplant on toast than guacamole. Guacamole is not a breakfast food.
Do you know what is a breakfast food? Or indeed an any-time-of-day food? Strawberries. Also, strawberry and sugar sandwiches, which you make by spreading butter on bread and adding strawberries (sliced) and a tiny bit of sugar. (I know, it's perilously close to sugar on toast, but the crucial distinction is that it's not toast.)
Do you know what is a breakfast food? Or indeed an any-time-of-day food? Strawberries. Also, strawberry and sugar sandwiches, which you make by spreading butter on bread and adding strawberries (sliced) and a tiny bit of sugar. (I know, it's perilously close to sugar on toast, but the crucial distinction is that it's not toast.)