The first syllable is the important part, anything goes as long as that matches the last syllable in the previous word, and as long as your answer doesn't end in ん. (Unless we make that one a bit of a "joker card" and said it could work with everything that starts with the "n" sound - なのにねぬ. This isn't really part of the original game, though, I guess. Thread starter decides this one.
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A problem that we're likely gonna see here soon is duplication, words being posted multiple times. People won't want to read X pages to figure out if theirs has been posted already..
Anyway;
国 くに
(Country, nation, etc.)