Michael Horden, if I might add, is the definitive Marley for me forever. Horden was great in everything I ever saw him in, starting with Sim's Christmas Carol. A favorite character actor of mine.
Another vote for George C. Scott. One of the things I liked about his portrayal was that he treated all the old familiar lines as though Scrooge said them more for his own amusement and to see what kind of shocked reaction he could get from people than because he really believed them. Thus his transformation at the end seemed easier to believe than in some other versions.
