I gave Irene the gun, if she would rather end her own life than become a walker she should have that right.
I also shot the girl in the street, I wasnt about to stop caring about the fate of others simply to make my life easier. In the zombie apocalypse people need to try to help others whenever possible.
I couldnt make Kenny shoot Duck. Even though Kenny seems to turn on you pretty fast and becomes a real dick once you start disagreeing with his decisions, what father should have to shoot his son?
And at the end I had Clem shoot Lee because becoming a Walker seems a fate worse than death, and Lee would not have wanted to become a Walker.