'I cannot read the fiery letters,' said Frodo in a quavering voice.
'No,' said Gandalf, 'but I can. The letters are Elvish, of an ancient mode, but the language is that of Mordor, which I will not utter here. But this in the Common Tongue is what is said, close enough:

One ring to rule them all, one ring to find them,
one ring to bring them all and in the darkness bind them.

It is only two lines of a verse long known in Elven-lore:

Three Rings for the Elven-kings under the sky,
Seven for the Dwarf-lords in their halls of stone,
Nine for Mortal Men doomed to die,
One for the Dark Lord on his dark throne
In the Land of Mordor where the Shadows lie.
One Ring to rule them all. One Ring to find them,
One Ring to bring them all and in the darkness bind them
In the Land of Mordor where the Shadows lie.'

Blue bold text taken from Lord Of The Rings, Book I, Chapter 2, "Shadow of the Past." Copyright 1955, 1965 by J. R. R. Tolkien, renewed 1982 by the Tolkien Estate.

Since it isn't likely to attract any Orc here, I will do what Gandalf did not, at this point, anyway -- here are the words in the Black Speech of Mordor, transcribed into our letters:

Ash nazg durbatuluuk, ash nazg gimbatul,
ash nazg thrakatuluuk, agh burzum-ishi krimpatul.

The sound of that IS kinda creepy, isn't it? It's said that Tolkien really rather despised this language, though he invented it. There are only maybe a couple dozen words in the Black Tongue in all of Tolkien's works, so it's hard for anyone to expand on it and use it.... I wonder if that was by design?