This seems to becoming about the personality of the OP on threads other than this one. The question prima facially, is about the lens used to take pictures of people. And can't we all agree that the first choice of the poll is correct when that is the definition of portraiture - pictures of people. However if you mean the old-fashioned term, then a much narrower range of focal lengths work best. The exact lens to use depends on several things. The distances involved - not only between the camera and the subject, but also between the subject and the background. The parts of the person to be photographed - tight head shots vs full length and group portraits. The style of portrait - formal with studio lighting vs grungy, punk, drunken master style. And everything in between.
One's portraiture style is a very personal decision.
I see a lot of APS-C digital shooters using an 85mm which has the same look as a 135 on 35mm film. I really like 85 for head and shoulders type studio shots, and anything between 35 to 180 for candids, depending on how tight I want to shoot and how close to my prey I am.