Fallout 2: you know when Chief Justice Marion/Mayor Marion/Sheriff Marion/Earl Marion tells you to go investigate the ghost town, and the people of Ghost Town want you to find the boy who ran away years ago? Well, being fed up with not being able to find the kid, I just sit back, wait, let Redding and Ghost Town kill each other, then proceed to loot their things, kill the survivors, loot some more.
I screwed all the Redding and Ghost Town quests on that one.

Can't really remember any specific mistakes since it has been a while since I've played Fallouts. But I do remember one that can be your greatest victory and greatest mistake at the same time in Fallout 2... Give Marcus bozar and go fight in caves or small corridors with Marcus standing behind entire team. I had Marcus blasting a pigrat with bozar once. Killed the bigrat for sure, along with me and every other member in team. Fun stuff ;)

Fallout2
I went to the second town(forget the name) and talked to durton. He called me a bag of gecko shit so I say "Gecko shit? Are you referring to what you eat or what your brains are?"
The whole town attacked me....

My brother's pulled a few smooth moves in Fallout before.
Once during the bar fight in the Skum Pit in Junktown, he figured nothing bad would happen if he punched Neal. His harmless little punch killed Neal and (with the bloody mess trait) spilled Neal guts all over the bar.
The funnier story involved the Ghost Farm and Modoc. He helped the people at the Ghost farm but forgot to talk to the guy at the bar back in the Den. So he didn't have enough proof to convince the mayor of Modoc that the Ghost Farm was friendly. So he went walking back to the Den to talk to the guy from Modoc in the bar. By the time he reached the guy, listened to his story, and walked back to Modoc, the mayor of Modoc informed him that they killed all of the inhabitants of the Ghost Farm... even the children.

Uhh....
Yea.
I went in and said "I see why you call this place The Hole"
He responds "Watch it!"
I respond "Or what?"
Cant walk in there without being attacked.
And I killed his prostitute. She started it.

Fallout 2: Got into a random encounter with Fire Geckos, decided me and Vic could handle them. Yeah, that really worked out well.

In Fallout 1, I went into the military base with a full party (Dogmeat, Ian, Tycho, and Katja).
Trying to get out of the elevator, Tycho always got in the way, so I had to summarily execute him.
And the rest of the party created a good buffer to survive the military base.

I saved as soon as i got the waterchip..... Had 2 days to get from necropolis to the vault...

I discovered that standing in front of a super mutant with a flamethrower while i have a no weapons wasn't a nice idea after all.
Thats awesome dude XD
actually pictured the character flying in my mind and the raider shouting
"ROCKET BOOGIE NO BOOGIE BACK!" XD

Well in fallout 2 I always seemed to be forgetting to make the character i want before being done and I had to redo the character creation process at least 5 times before I got it right.

My first time through Fallout 1 I learned the hard way that reading books in the Glow is a bad idea.

Probably my most royal screwup was creating a set of characters in Fallout Tactics for multiplayer, setting up all their gear, leading them into battle and then realizing I forgot to give them ammo.

At one point i wanted to just kill everyone inn Fallout1.
So with only The Master left to kill and equiped with top tec, i start my rampage.
I visited all the locations and started the killing.
Now at 650+ men killed my last stop was The BrotherHood of Steel.
The combat is really silly, eather you get hit for 10 dmg from the minigun or he crits you and hits you for 15.000! Had to save every turn lol.
Anyways, at the armory i think it was there are 3 Brothers inside and the door is locked. And whenever i walked (or sneaked) up to the door to pick it i would enter combat as if the brothers inside would somehow sense me coming. And you cant pick in combat... soo thats kinda haunted me forever... stil does ^^

i went in the glow without taking rad-x and inside i took my time to check all the corpses when i exited i had 1470 rem in me. i couldn't walk for half a day before my death.