This is a topic I never hear much discussion about, so I'd like to know what everyone thinks. Obviously, there's Falconetti from Dreyer's THE PASSION OF JOAN OF ARC. That's got to be way up there. And Emil Jannings was incredible in Murnau's THE LAST LAUGH. Orson Welles was pretty remarkable in CITIZEN KANE (although acting isn't necessarily the film's best aspect), and there's been a lot of talk about John Wayne's performance in THE SEARCHERS (although I never thought I'd be submitting Wayne's name for anything).
Anything else? It'd be nice to assemble a good, solid "Top 10."