TOD:
I will preface my selections by saying that my earliest memories of going to the movies were of three films: "Anastasia", "The Ten Commandments" and "War and Peace" -- all 1956 films. I saw the first two in theaters in Augusta, Georgia, and the latter in the small theater in Johnston SC (where I now live).
It is amazing to me how vivid my memories of those films remains from those first viewings although I have watched all three many times over the years.
That said, when I read lists of Hepburn performances, I seldom, if ever, see "War and Peace" listed among them. I have to express surprise for that, alone, because she is absolutely luminous as Natasha Rostova, and she is the very best thing about that film which is a very good movie considering the - at the time - unfilmable nature of the gargantuan Tolstoy tale. The Russians, of course, did film it...in a 431-minute adaptation. In 1956, that would not have played at all well in U.S. theaters.
My favorite Hepburn performances:
Rome Adventure
Sabrina
War and Peace
Funny Face
The Nun's Story
Breakfast at Tiffany's
Charade
My Fair Lady
Wait Until Dark
Two for the Road