Detour (1945, Edgar G. Ulmer) – only part of this is set in Los Angeles but it is certainly a classic and worth watching.
Mildred Pierce (1945, Michael Curtiz) – while this is also a melodrama it’s definitely also noir. The updated HBO version is far more melodrama.
Sunset Boulevard (1950, Billy Wilder) – what happens when a demented cougar (one of the original ones – far before Mrs. Robinson) falls for a second rate screenwriter? A cautionary tale of younger men using older women in Hollywood.
Angel Face (1952, Otto Preminger) – spoiled rich-girl Jean Simmons toys with Robert Mitchum‘s life for fun while attempting to kill her step-mother and destroy any other female competition out there. A great over-the-top performance by Simmons and a fun watch.