I'm at the point where I have to kill Private Crenshaw. The only problem is that I don't want to gain any NCR infamy in the process of doing it. Is there a way to silently kill him?

http://www.gamesas.com/index.php?/forum/108-fallout-new-vegas-cheats-hints-and-spoilers/

i juist did this quest today and if you have a high enough sneak when you talk to him about being a prankster then chose the sneak check one and it automaticly drops a gernade just run so you dont get hurt and i didnt loose ncr rep