Toast Crumbs in the Butter
I hate it when people take too much butter on their knife, spread it on their toast and then scrape the unused butter, which usually contains toast crumbs, back into the container. Please learn how to take the right amount of butter on your knife for each slice of toast; if you take too much you should take responsibility of your lack of judgement and use or throw away the surplus butter, not contaminate the butter with toast crumbs! It is vile, corrupting, selfish and ruins the day for other butter users.
When I come to butter my corn or other food requiring butter, I do not want toast crumbs on said food; in fact, even if I am also buttering toast, I do not want your old toast crumbs on my newly buttered toast!