I'm feeling kind of lucky right now. I've seen so many of my favourite chars die horribly (Ike, Doyle, Anya, etc.) and for once, I'm feeling, "yeah, okay, that's not too bad."
I mean, I knew they were going to kill off someone. And doing a breakdown of the characters, I came to the following results:
They mustn't kill Hurley or Sayid.
If they killed Sun, Jin, Claire, Charlie or Sawyer (yes, damn it, the man is growing on me) I'd be sad and probably cry. Also, killing Claire would be creepy considering the maybe-evil baby.
Walt is a well-acted child char, which would make it a terrible pity to kill him off.
Michael is played by Harold Perrineau, whom I like on principle even though I'm not very attached to his character.
Locke is too important to the mystery to kill off - it'd leave a bunch of questions unanswered and really annoy me.
They weren't going to kill off Jack or Kate, no matter how much I might want them to.
That leaves Shannon and Boone. Of those two, I prefer Shannon - she's shown more of a personality, even if it is a bad one. So Boone it is. In truth, I find the decision a bit cowardly - I would have expected the show to rip out my heart and stomp on it a'la Joss Whedon.
...Of course, I still would have preferred it if they'd cut off his leg instead, but I can understand why that would have been terribly impractical. :-)