Brother of famed child actor and director Ron Howard, Clint has appeared in over 200 films and television shows. (At least 17 of those films were directed by Ron Howard. See IMDb.) He has a very memorable, um, non-leading man face, and he generally plays a regular Joe just doing his job in the background or someone who is just kind of...off. MTV once awarded Mr. Howard their jokey version of a "Lifetime Achievement Award." But when he won he gave this utterly sincere speech, because he was truly touched by the recognition. They retired the award after that, and Clint was forever endeared to my heart.
Yes, another brother, but this time the brother of comedian Bill Murray. His gravely voice is his most defining characteristic. He generally plays good-natured, blue-collar or skeezy boss. (See Groundhog Day and Christmas Vacation.) I particularly like his role in Waiting for Guffman.
Cherry Jones has won awards for her theater work, but when she's in films or television she somehow falls more into the character actor world. I've seen her mostly play no nonsense, authoritative roles. (See Signs and Ocean's Twelve.) She's also lent her warm, subtly twangy voice to several audio books. She currently has a recurring role as a psychiatrist on NBC's Awake.
I'm pretty sure the only thing Danny Trejo plays is a Hispanic gangster or criminal. It could be because that was his real life for many years, but then he got clean, changed his life, and kind of stumbled into the movie business. There's just something about his face that I love even though I'm supposed to be terrified. On IMDb I counted 22 projects that he is a part of that are being released either this year or next.