...with an NPC or other situation in the game where you went for your gun and opened fire under the guise of rp and then went with it?

I'm doing a playthrough of FO2. I am playing a CO that is very focused on being the glorious hero of his tribe, the action hero macho type that's as good with his fists as with a gun and always has a smart thing to say in the face of danger. I get to Modoc (I HATE Modoc) and I'm playing the Ghost farm mission and then Jo tells him that he lied to him about the Geck to get him to go on that ridiculous mission, and my CO drew his .44 revolver and blew a sunroof sized hole in Jo. Luckily it was the dead of night and my party did not have to do a running gunfight to get out of town. But it felt right, so I did not reload. I'm interested in your war stories, so to speak.

You killed him?
You evil.

Yes, he lied to you so that he could get your help to save his town, but he didn't need to die for it.