Mister Ski
Super Freak
That would take some major you know what to do. It would IMO be the beginning of the end for this show to kill off a character like that.
I dunno. Rick is really failing at being a competent leader and has caused more grief and death than he's prevented. Seems like every time they start to make him the badass, he makes some DFI decision and ****s it up for everybody. While I don't think they'll kill him off, I don't think it'd have nearly the impact you're claiming. At this very point, killing off Daryl would hurt the show more.
The more I think about it, the more I think they could and will do it. They have performed the same type of character assassination on Rick as they did with Andrea last year. The writers made Andrea so unlikeable that they were practically forced to kill her off. They are doing the same thing with Rick by making him so much more weak and indecisive than his comic counterpart. I hope I am wrong as he is still my favorite character, but even I have to admit it is hard to find much to like about him these days.