Vector is by far my favorite.
First and foremost, his voice, accent, and speech patterns are so soothing. He's intelligent, open to other cultures and a true diplomat. I find him being part of the hive both intriguing and appealing. He's also wholly devoted to my agent(s).
I can't think of anything that I don't like about him. He's actually very different to men I find attractive IRL and yet I still think he's perfect the way he is.
I wish I could encounter him on other classes.