Yeah, Marlowe and Spade... I guess it should really just be "Humphrey Bogart". He is the king of the classic noir detective film. It's hard for me to pick between the two, as they're pretty similar characters. Spade definitely is less dark and cynical with more humor in his personality. For the dark brooding and more traditional type, go with Marlowe, for the less serious but still pretty grim one, go with Spade.
Or we can split Phillip Marlowe in two and get this.