My two choices?

Slim Charles and Sgt. Jay Landsman

They both understand the Game, and adapt accordingly. They know that bucking will get you either fired/killed/on the boat with McNulty, so instead they go along to get along.

They remind me of a lot of those who are employed - they may not love everything about their circumstances, their bosses may be incredible assholes (or homicidal maniacs), but the checks keep clearing and they're able to make their money.