Man, it's been forever since I've done one of these, not that anybody cares (except Snaps. and besides the occasional new-IP sneak attack in which she exposes more Rooskies and their Western minions, she's long gone).
Suspense! Howard Da Silva in the Cornell Woolrich story You Take Ballistics (13 March 1947). Da Silva was Nat the bartender in The Lost Weekend and Louis B. Mayer in Mommie Dearest. Tons of other stuffs I'm sure, but that's all I remember him from. And by God, that's an uncredited and pre-Dragnet Jack Webb as Coleman, da moiderer. Funny line from Da Silva just after he arrests Coleman: "Three months later, Coleman went to the chair."
And since we mentioned it, Dragnet. This one is called The Big Actor (10 August 1950). And don't forget, it's wise to smoke Fatima.
And just for a changeup, perhaps the first adult sci-fi program on radio, Dimension X: First Contact (8 September 1951).