First thing we do, I snipe every single Legion member in Cottonwood Cove with a headshot, then I free the captives. All going good so far, there's a dead legion soldier floating headless around the docks. Got a good lulz out of that. Boarded the raft and headed into the fort.
First thing I do when the guards charge me is go into VATS, get a critical strike on the first guy charging at me and watching all of his brains fly off toward the guy behind him, whom promptly loses his head as well. Then with my restored AP, I pull off another quick headshot on the next guy. And the next. And the next, until 20 AP recharges don't suffice. Then I just use Cass as a distraction to pop off manual headshots. All of the gate guards dropped within a few seconds, and I proceeded up the hill path, popping headshots and watching the gory beauty fly everywhere.
Eventually I killed every last Legion member in the camp and stormed into the big man's tent. Several headshots later, I single handedly ended the war. Or I would have, had they given me the option.
My second best moment was in Vault 3, after I talked my way through the front door, walked up to the big boss Fiend, pvssyd him up and then attacked. After listening to his smug reply that I'm not powerful enough to topple him, I soundly disproved his theory with two shots to the head with my rifle. I turned around immediately and shot his two guards, also in the head, and calmly strode past the dogs while reloading and leaving them to ED-E and Cass. Two or three more fiends pop around the corner, one with a flamethrower. The flamer lost his head quickly, and so did the chick charging me with a... Golf club?
Needless to say, there were so many headless bodies and skull fragments scattered around Vault 3 that the previous inhabitants were suitably avenged.