I voted for Jolee. He's fun, he's funny, and he allows my personal lightside tendencies to enjoy a little of the darkside powers.
I like Carth a lot, and I don't understand the hatred for him. He's pretty realistic, and has a good story.
I even like T3-M4, but that's only from a powergaming perspective. I sub him in instead of Carth when I am adventuring indoors.
HK is cool and funny, but the powergamer in me can't use him too much.