The one thing that kinda got to me was the NCR soldiers just outside camp forlorn hope with their arms and legs amputated laying near a frag mine. Seems quite extreme but effective.
The slightly confusing thing about this is that, as a random speech thing, one of the NCR soldiers in Forlorn Hope can tell you to be careful about the Legion using bodies as traps. But when you find them, you can't loot them, which is normal for interacting with a living person. I think the intent was for them to be alive, which is far more brutal and fitting, but that speech thing kind of mucked up my view on it.
Emotional stuff... you can assume bad actions on the part of lots of people in the Wasteland, but anytime I had a chance to shower holy vengeance on a known rapist/slaver, I was very much in my happy place.
On the flip, when Boone tells you precisely how he knows his wife is dead is up there. Hearing Chief Hanlon speak and knowing as soon as he starts what's going to happen. Helping Veronica only for nothing at all to work out like she wants (Felicia Day's voice work really makes this happen).
To get away from answers everyone else has given: I started a second character designed to be a horrible person. After finishing Run Goodsprings Run, I looked around at Trudy, Sunny, Easy Pete, etc., all laying there, and I felt absolutely awful.