Character actors are those secondary reoccurring figures in movies; their faces are familiar but their names, often, are not. They generally have distinct personality traits that stay with them over sometimes long careers. When they show up in this film or that, there is often a pleased sort of ah from the viewer, who is not always prepared for their appearance.
Actually, the four I've chosen aren't exactly typical in that they are more famous today than a lot of stars who came and went. But there's a reason for that. They represent character acting at its best, and their contribution to film is deep and lasting. They are essential elements in the Dark Energy chemistry.
If these four have something in common, it's a loose-cannon sort of thing. When they show up, anything can happen. If some of their movies aren't up to playing out that possibility, it certainly isn't the fault of this lot.
Each of them has presence. In chapter 13 (Universal DVD) of Touch of Evil, a dark and malevolent angel enters a dark room where Janet Leigh is in peril, trapped on a bed by young leather-jacketed bad boys. The camera follows this angel as she drifts across the room and delivers her line: "Let me stay. I want to watch." Don't we all. It's why we're gathered here today.
But it takes a Mercedes McCambridge to really, really get it across.