I like him in the Leones, especially in A Fistful of Dollars and The Good, the Bad and the Ugly (a bit less so in For a Few Dollars More)
Also like him in non-spaghetti westerns and the Dirty Harry movies. He was only really great when directed by a master director: Leone, Siegel. They knew exactly how to use him and his magnificent screen presence to maximum effect. One of his better performances of his later career, is in Wolfgang Petersen's In the Line of Fire.
I never cared much for his work as a director. Mystic River is one of the few Clint directed movies I really like. I think he has too much controll over his films: they usually are very uneven, with some good scenes or ideas, but overlong and with too many weak or superfluous scenes. People involved in his movies dare not tell him when things aren't right, I guess.