I just went through my list of my 100 favorite films, and these are the ones that are completely in black and white (although several of my favorites are both color and black and white):
All Quiet on the Western Front (1930, U.S., dir. Lewis Milestone)
Camille (1937, U.S., dir. George Cukor)
Casablanca (1942, U.S., dir. Michael Curtiz)
Citizen Kane (1941, U.S., dir. Orson Welles)
Dr. Strangelove (1964, U.K., dir. Stanley Kubrick)
Duck Soup (1933, U.S., dir. Leo McCarey)
Freaks (1932, U.S., dir. Tod Browning)
The Great Dictator (1940, U.S., dir. Charles Chaplin)
It’s a Wonderful Life (1946, U.S., dir. Frank Capra)
King Kong (1933, U.S., dir. Merian C. Cooper)
La Jetée (1962, France, dir. Chris Marker)
La Strada (1954, Italy, dir. Federico Fellini)
The Last Picture Show (1971, U.S., dir. Peter Bogdanovich)
M (1931, Germany, dir. Fritz Lang)
The Maltese Falcon (1941, U.S., dir. John Huston)
Modern Times (1936, U.S., dir. Charles Chaplin)
Psycho (1960, U.S., dir. Alfred Hitchcock)
The Searchers (1956, U.S., dir. John Ford)
Seven Samurai (1954, Japan, dir. Akira Kurosawa)
The Third Man (1949, U.K., dir. Carol Reed)
The Treasure of the Sierra Madre (1948, U.S., dir. John Huston)
I have no idea which is my favorite drama and which is my favorite comedy.