Movies:
* Tarzan's Magic Fountain (1949): He played the titular character, Tarzan, opposite Brenda Joyce as Jane.
* The Thing from Another World (1951): This science fiction classic features Agar as Captain Patrick Hendry, the military leader who confronts the alien creature.
* The Mole People (1956): He starred in this horror film as Dr. Thomas Craven, a scientist who discovers a civilization of subterranean humanoids.
* The Incredible Shrinking Man (1957): Agar had a supporting role in this science fiction film as a friend of the protagonist.
* The Land Unknown (1957): Agar starred as Dr. Hal Jeffrey, an explorer who encounters prehistoric life in the Antarctic.
* The Angry Red Planet (1959): He played a scientist on a Mars expedition in this science fiction film.
* The Leech Woman (1960): Agar starred in this horror film as a scientist who discovers a woman who feeds on human blood.
* The Brain That Wouldn't Die (1962): He had a supporting role in this horror film, directed by Joseph Green.
* The Madmen of Mandora (1963): Agar starred as a man who discovers a hidden civilization in the African jungle.
* The Return of the Fly (1959): Agar played a scientist who is investigating the mysterious death of his brother in this sequel to the classic film.
Television:
* The Adventures of Jim Bowie (1956-1958): Agar played Jim Bowie in this popular western television series.
* The Lone Ranger (1955-1957): He appeared in several episodes of this classic western show.
* The Twilight Zone (1960): Agar starred in an episode titled "The Parallel", playing a man who discovers he has a doppelganger.
* Have Gun Will Travel (1957-1963): He appeared in several episodes of this popular western show.
* The Virginian (1962-1971): Agar had a recurring role as Clay McCord, a rancher and friend of the protagonist.
* Bonanza (1959-1973): He appeared in several episodes of this popular western show.
* Gunsmoke (1955-1975): He appeared in several episodes of this long-running western show.
This is just a sampling of his extensive work. He appeared in many other movies and television shows, often playing rugged and adventurous roles.
You can find more information on his career on websites like IMDb.