The good ones tend to be well known. There's no 'black opening' though. There are two players in every opening. So you will need a different good black move for each of the main white first moves.
a good black opening?

If its not very well known, its not very good. Not very well know is easy to come up with if you don't mind losing. Plenty of people here will give you their made up openings but most presume poor play by one side.

SInce Kramnik is behind perhaps you should suggest them to him.
Yes, and i think Anand can tell you some...

The Latvian, Modern, etc are all known (even the Ptero) with a body of theory. How good they are is another question. Other than one GM I can recall off hand, how many play the Latvian and Ptero against their peers? Modern is well known, respected with a huge body of theory.
I think you must prepare an opening's repertoire, first. You can prepare your own opening's repertoire in http://www.ecochess.com
I see you later
does any one have one thats not very well known