9. Damnit could be used, though you're better off with "dammit" or "damn it". As per Wiktionary: damnit. Nonstandard contraction of damn + it. Interjection (especially southern US) Common misspelling of dammit. Edit: As my answer points out, "damnit" is considered a misspelling of the more popular "dammit", which confirms ЯegDwight♦'s data. More @Wikipedia
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