Would you hesitate to kill a man if...

Your life, or someone else's was in danger? I've have seen it in movies thousands of times; The "good guy" is put into a situation where he needs to shoot the "bad guy". However in nearly all of these scenes, the "good guy" hesitates. Personally, the thought of having to take another person's life (necessary or not) scares me. It would definitely haunt me for all my life, no matter what type of person they were. It's funny, because I had a dream last night where I was kidnapped and I knew this guy was going to kill me. I end up finding a gun, pointing it at him but I can't shoot, I run away instead. I got the idea for this thread from Jake's, were he talked about a guy getting shot for simply going in someone's driveway, and it scares me how easy it is for someone to just pull the trigger and end someone's life for such petty reasons. So, would taking someone's life be easy for you? Hard? Would you think twice or not look back? EDIT: Also, the question isn't if you would do it or not, but if you'd hesitate. Would doing it be easy or hard?