With Eastwood in it, Million Dollar Baby. The sheer elegance and precision of Eastwood's direction is a joy to watch and the fact that it has the best performance of his career doesn't exactly hurt. White Hunter, Black Heart, The Bridges of Madison County, The Outlaw Josey Wales & Unforgiven would all be up there as well.
As director but not star it would probably be Bird, Eastwood's superlative bio of jazz legend Charlie Parker. I saw it twice in some art cinema back in 1988 and left more convinced than ever that if critics persisted in dismissing Eastwood as just some actor turned director then they simply didn't know what they were talking about. As William Goldman put it when he saw Bird at Cannes that year: 'It was by far the outstanding directorial work of the fortnight. The only stigma being Eastwood and our memories of all those action films. How dare he attempt a serious movie? And bring it off. I believe that if Francis Coppola had directed it, frame for frame, the critics would have put him back on top with Woody Allen. And if Allen had done it, they would have elevated him up alongside Welles.'
On the other hand I was seriously impressed by the oppressive power of Mystic River so much so that it may just tie with Bird for first place. However I have a feeling Flags of Our Fathers & Red Sun, Black Sand may displace both before too long.
