This cover from April 2002 is by far my favorite. Annie Leibovitz shot the image, and it actually has a fashion presence to me.
The March 2004 cover by Mario Testino isn't bad either. Gorgeous dress!
The January 2007 cover, which was frequently paired with Jennifer Aniston's Vogue cover (in which Aniston also posed in a red dress). Celebrity feuds really do not belong in the pages of Vogue. I considered this cover (and the story) a low-point.
(**cover image from www.shoppingandinfo.com**)
And we have the December 2010 cover. I love the blue background and hot pink type. Oh, and the Tom Ford dress. But that's about it...
(** all images from Google search**)