Gangsters Stringer Bell is obviously an aggressive strategist: ENTJ (extrovert intellectual judger), the type of the general or business wheeler-dealer. Like with most ENTJs he uses his clothes to express his intention, and he makes sure they are different from the people around him (cf. Servalan.
His boss, Avon Barksdale, is much more introverted and even meaner. He's a lone soldier rather than a general, and he was a boxer when he was growing up. I think he is ISTP (introvert tough minded and sensual) - almost the opposite type from Bell - this is the same type as Steve McQueen or Clint Eastwood. He doesn't express his feelings very well but he has intense loyalty to a very small family group.
Blakes 7 fans - this is like Soolin was running an urban drug gang, with Servalan as her strategist.
I think DeAngelo is ISFP or possibly INFP - introverted and dominated by feeling - self-sacrificing and has difficulty compromising.
Police - McNulty seems quite obviously an extrovert sentimental sensualist - ESFP (like Vila but more out of control). His friend Bunk Moreland is probably a similar type, but a bit more hard-headed. Perhaps ESTP or ESTJ.
Freamon is an introverted idealistic judger - INFJ - the wise advisor (Cally).
Prez is an introverted monitor-type - ISTJ - intense need to belong and serve, which he maintains by careful attention to detail, and solitary working (a bit like Travis, and like Travis, when he had no leader, he became violent).
Lt Daniels I'm not sure yet. I want him to be ENFJ like Blake, but I haven't got it straight yet.
I think Kima is the same type as Avon Barksdale - she's the Soolin of the Police, or if you like the Steve McQueen.
Yeah, I had to get this down, sorry.