Obviously, these are some of my favorites, and I've certainly left lots of worthy actors off this list. If there's anyone else you wish had made the list, let me know in the comments!
Best known for his role as Frances McDormand's vengeful, cuckolded husband in the Coen Brothers' 1984 classic Blood Simple, Hedaya's one of those actors who seems to radiate menace. In this scene, the man who's been sleeping with his wife -- and who works at his bar -- asks him for back pay.
... was a child actor -- he famously played Gregory Peck's son in Gentleman's Agreement -- and besides his fame for co-starring in Quantum Leap with Scott Bakula, he's probably best remembered for his roles in David Lynch films -- especially this unforgettable scene in Blue Velvet, where he plays Ben -- "one suave fucker!" NSFW, obviously!
Danny Huston is one of those faces you see all the time, steals every scene he's in, but almost never gets the leading role. He is, in fact, the son of Legendary director John Huston, and he's appeared in more movies than I can possibly name here. One of my favorite roles of his is as a possibly-insane and brutally poetic outlaw in the absolutely stunning Australian western The Proposition (a film full of wonderful actors -- John Hurt, Emily Watson, Ray Winstone). Just a warning: this scene is rather violent.
The oldest actor ever to be nominated for a best supporting actor Oscar -- for his role in Into the Wild -- Holbrook was previously best known for his one man show about Mark Twain.
The Swedish-born actor with a face of stone, he pops up in films left and right these days -- especially films by the Coen Brothers. He was Wood Chipper Guy in Fargo and one of the Nihilists in The Big Lebowski. (So yeah, some swearing.)
Gary Cole's been in bazillions of movies and TV shows, but he'll be forever associated with just one role -- as the boss, Lumbergh, in Office Space.
He's impossible to forget as Marty McFly's father in Back to the Future -- and pulled a Joaquin Phoenix of his own a few years later on The David Letterman Show.
Probably my all-time favorite character actor, John Turturro can make almost any movie worth watching. Everyone remembers him from The Big Lebowski, in which he plays -- I'm not sure what to call it -- a bowling mariachi gangster? In any case, this brief-but-legendary scene is definitely NSFW.