There are times that I wish I could do something more than once in Fallout. These are:
Telling Sarah Lyons that I dont want to be in her little club.
Blowing up the citadel.
Killing Three Dog.
Killing Paladins.
Enslaving any member of the Brotherhood of Steel.
Leading my own attack against the citadel with Jericho while we are both wearing Enclave armor.
Talking with President Eden.

I couldn't agree more.

The list would keep going if bethesda didn't force us to join the Brotherhood of steel.

Raiding a supermarket. Unless there IS another one, in which case tell me now!

I wish I could lead another attack against the Enclave's Adam Air Force base again. So fun. Shaun(My character), Fawkes, Charon and Star-Paladin Cross, in an adventurous attack against the base. It was a memorable moment. We were the Brotherhood's last hope(However, they would eventually regret, sending us to do the job, as we had planned to bomb the Citadel, in the end). We travelled through the metros, as the four of us, had a hell of a time, getting past all of the Feral Ghoul Reavers. However, I managed to show the access card to M.A.R.G.o.T, which made all of the robots, in that metro help me in defeating the roamers. I thank M.A.R.G.o.T for that. When we reached the subway, it was a hell of a fun ride. We had never experienced "riding" before, so it was fun for all of us. Then we travelled more into the metro, as we defeated Enclave soldiers and hellfire troopers.

After leaving the metro and destroying 2 of those Enclave Vertibirds...we had seen the actual base, itself. It had only been fatal for Cross...as she had been sick, almost that whole trip. With that...she knelt down and took her final blow...in the hands of the Enclave. They killed her. I kept her Brotherhood Of Steel holotag in memory of her. I never gave it up. With only 3 members left, we killed off the rest of the goons, guarding the base and went inside. It looked very protected. It was.

Hologram shields, guarding their supplies, made it very difficult to gain them. I was hungry. Fawkes was hungry. Charon was hungry. We had camped inside of that base, for a good 2 days, undetected. However...we had met a friendly man, there...who was actually the technical engineer of the Enclave. He had been working, for them, for a long time. He managed to disable, some of the hologram shields, which gave way to Stimpaks, RadAway, Food, Water. All the supplies needed for my team to carry on. I thanked him, as I moved forward.

We ended lives of many. Many Enclave soldiers. Many Enclave Hellfire troopers. And many Enclave Generals, as well. The pain had been getting to Charon, though. I could see it in his beady little eyes. He had been killed by a remnant of the Enclave, that very moment. Fawkes had snapped. He went full-out rage, on almost everyone in that building. We had eventually killed out everyone in the mobile base crawler. I kept Charon's Combat Shotgun, as well. A Shotgun, that will nbever ever be replaced.

After bombing the Citadel, and being tooken back to it, by our so-called friends...Fawkes and I had finished every damn one of their lives, in provoked attack. After that, we had scoured just about everything in their armory, as well.

Fawkes and Shaun Tasco. Friends to no one.

I'd love to be able to repeat the quest "Stealing Independence" again, there is just something about Button Gwinnet that makes me admire him. And I'd love to help him again if given the chance.

Play Fallout 3 for the first time again.

Killing the raiders at Evergreen Mills again, rescuing Reilly's Rangers, and killing the super mutants that attack Big Town.

letting the gouls in tenpenny tower.

I would like to talk to President Eden more.

Killing 3 Dogs fun too.

Play it without having read anything on the internet.

Stepping out of the vault 101 caves for the first time. Now I know to expect the adjustment to the light, but the first time was the best.

Killing Butch.
Killing the Overseer (Mack, hate that [censored])

And heres a personal moment of mine. I was being chased by 4 Muties, one with a mini gun. I only had Col. Autumns 10MM pistol on me with barely any rounds left, and a few grenades. Then I see a squad of Raiders coming my way with a bunch of wrecked cars in my view on the road. So I run off to the side, then the Raiders start shooting the Muties, the muties start shooting the Raiders, as they approach the wrecked cars I throw a grenade and duck down to watch the fireworks... What a beautiful sight that was. They all died, I walk away victoriously crippled.

Adding to OP's list which I completely agree with, I could watch the Enclave land in Jefferson Memorial a thousand times.