Do you have a budget? My first recommendation would be the Schoeps CMIT5U, but I get the feeling that $2,100 for just the mic is a little out of your price range.
What other audio gear do you have?
Do you have any audio experience?
Where will you be shooting, primarily?
As always I recommend that you hire a sound professional or hook up with a talented up-and-comer. Barring that, instead of buying I recommend that you rent.