I love Lost. I have been a faithful viewer since the beginning. Even when I lived a year in Prague, I watched each and every episode on iTunes. I used to be obsessed; I used to go to all the blogs and forums and websites to read and discuss theories. I'm too busy for that now, so I just watch the show, but I still enjoy it immensely.
I have come to the conclusion that, much as I love the many other characters on the show, my favorite is Ben Linus.
He is the most complex character on the show, and the most fascinating. It's so hard to tell when he is bluffing, and you want to believe him, even though you know he usually is bluffing. He's the "bad guy" most of the time, but not always. Sometimes the way he rolls his eyes shows deeper facets of his character, and he can arouse feelings of anger and hatred as well as pity and sympathy in the viewer.
And because of all that, he's my favorite character.