what's your most memorable vanilla quest from fallout

Tranquility lane like every one else. i loved Dr. Braun

three card bounty, i love hunting down the fiends with 1st recon.

Going into Vault 03 when you have to find that NCR ranger and you get to slaughter like 200 fiends

You Gotta Shoot 'Em In The Head. I love the backstory to this quest and the different directions it can go.

The most memorable quest that I played in the vanilla Fallout games is easily the final mission of the vanilla Fallout 3 when the player is battling the Enclave for control of Project Purity. It was an epic large scale battle. Liberty Prime was so awesome especially when he threw mini nukes off his back at the Enclave and yelled his communism one liners. The ending of the quest was so emotional especially if the player chose to be the one to activate the code. Revelation 21:6. I am Alpha and Omega, the beginning and the end. I will give unto him that is athirst of the fountain of the water of life, freely. When I put in the code and realized what it all meant and how it tied in from the quote at the beginning of the game when you were a baby. It was just such an emotional experience, especially when I thought the player died and the epilogue played and you had good karma. Fallout New Vegas just lacked the emotional connected that Fallout 3 had in my opinion and I am so excited to see what Bethesda does next with Fallout 4. I truly hope that they return with an equivalent or even better story than Fallout 3. Anyway haha, that is why the last mission is my favorite in the game.

My favorite quest is I put a spell on you Spoiler.
I loved finding out who the culprit  was and racing  to the monorail to disarm the bomb.

In FO3 the "Wasteland Survival Guide", specially the part where you have to go to the Superdupermart. Lots of fun exploring there and scavenging whatever is available

As for FNV, "Crazy, Crazy, Crazy". Exploring Black Mountain surrounded by all those muties is a great experience

my favourite is the battle at hoover dam in fallout new vegas

I loved the assassination of President Kimball. Just that feeling using a sniper rifle and blowing up his head is great.