And Polish polish polishers polish Polish polish.
Martha Washington was the first First Lady.
Cosmologists now think they know what happened during the Universe’s second second.
Joe got the first third of the pie, Mary got the second third, and I got the third third.
What what?
[sub]in the butt[/sub]
Not, never, cannot, possibly, neccessarily.
“Red”, as in, “That is a red red”, “That is a red red red” and so on (and so on for similar words).
I’d like to know if “all”, or “every” works. The most plausible examples I can get are the sentences “All all round things” and “All all”.
“Tut-tut, don’t pooh-pooh ‘unknown unknowns’”, Mr. Rumsfeld chided the press corps.
You would need a word that, like the thats of the OP and the buffaloes of the classic example, can function as two or more parts of speech that work well together:
[ul]
[li]Hampton Roads’ roads and bridges are congested during rush hour.[/li][li]After it leaves Manasses, where does Bull Run run?[/li][li]The committee bases bases’ viability not on political pull but on defense needs.[/li][li]Leave the foam rubber pillows up there; get the down down.[/li][li]The law prohibiting left turns turns ten tomorrow.[/li][/ul]
Is dick a dick or dick Dick or Dick a dick?
Okay that one is a rerun from another thread.
When Elmer Fudd shoots his shotgun, watch the duck duck.
One could argue that those are actually different words which happen to share the same spelling in modern English. The noun and verb come to us through different etymological paths (albeit with the same origin).
William is a lawyer who intends to encourage people write up documents pertaining to your property after death. Will will will wills. When he does his own, Will will will Will’s will.
A number of tennis losses in one tournament were bad for Sharpova. That set set set her back.
Though those kinds of examples, fun as they are, don’t really count, since the “wills” and “sets” have different meanings and aren’t really the same word.
“Never, never underestimate the power of desire.”
That’s true. But you could argue that the OP’s example also employs different words. “That that” uses the conjunction *that *and the pronoun that. Different parts of speech, different meanings (to the extent that a conjunction has any meaning).
Likewise, with “had had” and “do do”, the other examples that have satisfied the OP, the first *had *is an auxiliary verb that has nothing to do with having something, like the second had does. And the first *do *is also an auxiliary verb rather than meaning to act in some way.
Probably the only cases where it really is the same word twice are when a word is repeated for emphasis, but then there’s usually a comma between them.
Oh, details details…
Yeah, yeah. :rolleyes:
You want to see what people are up to, to see if they can come up with sentences that make sense?
Should you use a preposition to end a phrase with, with the wide choice of words available in English?
The ancient rocks of the Australian Shield may be found down under Down Under. 
No, there’s the one I mentioned back in post 77 of this thread:
Great great grandfather. Great great great great grandfather. And so on back as far as records go. Same word, same meaning, and as many recurrences of it as you can stand.
Well OK, but it ought to be hyphenated, so not exactly separate words. Not sure if that meets the OP’s criterion.