Elisha Cook Jr was a good character actor, usually cast as cowardly criminals or neurotics, and usually was killed in every movie he was in. He's probably best known for playing Wilmer the "gunsel" in the 1941 version of The Maltese Falcon, Stonewall Torrey in Shane (he get's killed by Jack Palance), and as Capt. Kirk's lawyer Samuel T. Cogley in the Star Trek episode Court Martial.
Richard Widmark did several radio shows in the late 1930s and early '40s, but made a big splash in his film debut as the sadistic gangster Tommy Udo in 1947s Kiss of Death, for which he was nominated for an Oscar. He played in the noir films Panic in the Streets and Night and the City, and the Westerns Yellow Sky, The Alamo, and Death of a Gunfighter, to name a few. He made 60 films from his debut until 1991.