D.O.A. (1949) - For noir fans, D.O.A. is a knockout, a peach, and for horror fans (often the same people!) it is the inspiration for Dead Heat (1988). D.O.A. is an absolute classic, especially in the “atomic noir” sub genre. It gets you right in the belly. As far as I know, all home video releases have been technically terrible since it’s in the public domain, so try to source the best looking copy - there are good HD files floating around the internet (cough rarelust cough) and there’s an excellent web version available to stream through a library-based service called kanopy which looks like it has been carefully remastered in blu ray quality.
Anyway, if you can dig D.O.A. (and I know that you can!), it is well worth seeking out two further gems by the same writer/producer/erstwhile director team of Clarence Greene and Russell Rouse: THE THIEF (1952), with Ray Milland excellent as an AEC nuclear scientist turned reluctant Soviet spy (which is on a par with D.O.A. for knuckle sweating tension and elegant narrative drive and is even more anguished, if that is possible), and the more formulaic but still massively entertaining WICKED WOMAN (1953). These three supremely confident low budget films constitute an extraordinary glimpse into a lost Hollywood of grimy satisfaction.