Belethor. When he says, "Do come again," the tone of his voice is such that I cannot tell if 1) he is supposed to be gay; 2) he is supposed to be obnoxious, or 3) bad voice acting.
Keep in mind that he says that to female characters as well. Right after talking about selling his sister (if he had one). Extremely creepy. Some people complain about the lack of brothels in Skyrim (which I, as a woman, find relieving). Maybe they should see Belethor to hear if he has someone to offer. ^^
Btw I even heard guards comment that he's sleazy. No kidding...