I was wondering about this one recently. "Fuck" in English is famous for being applicable in a wide, wide range of circumstances (none of them formal).
What word in Japanese covers a wide spectrum of possible meanings and uses like "fuck" does. Does not have to be a rude/vulgar term.
EDIT: half of you seem to have missed the point of my question. I don't need a translation for "fuck", I want a word as versatile. Maji is pretty good but I would've thought there'd be more contenders. Admittedly it's a vague question, but one for my izakaya zatsugaku collection.