The oddest one word sentence is…

"Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo"

The oddest part is that this sentence is grammatically correct!  Take another look.

“Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo.”

First created by a professor by the name William J. Rapaport.  Rapaport created this sentence back in 1972.  The sentence uses various meanings and parts of speech for the term “buffalo” and also the related proper noun “Buffalo”.  Doing this makes it quite possibly the hardest sentence to parse in history.

Most of know the word “buffalo” is both singular and plural for a bison.  “Buffalo” is also a fantastic and highly under city in New York on Lake Erie.  What you may not have known is that “buffalo” is also a verb.  It means “to bully, confuse, deceive, or intimidate.” Using these definitions the sentence can be read:

[Those] (Buffalo buffalo) [whom] (Buffalo buffalo buffalo) buffalo (Buffalo buffalo).
Still too hard to follow for those of us who don’t know “buffalo” as a verb. Refine once more:

[Those] bison from Buffalo [that are intimidated by] bison from Buffalo intimidate bison from Buffalo.
And once more:

Bison from Buffalo, New York who are intimidated by other bison in their community also happen to intimidate other bison in their community.

Buffalo is not the only word in English for which this kind of sentence can be constructed.  It is only the most famous. Any word which is both a plural noun and a plural form of a transitive verb will do. Other examples include dice, fish, right and smelt.

Beware of Buffalo buffalo, buffalo, for they may buffalo you.