50s style sports gear:
catchers mask/uniform
Football helmet/pads
cheeleader outfit
Rugby Shirt
referee outfit
Tennis Racket (as a melee weapon)
Weapons:
Bows & Crossbows
Bowie Knife ( for a game thats supposed to be all-american why is this not ingame?)
Attachable Bayonets
Food Related quests / easter eggs:
Find some grandma in a shack who sells apple pies (0 rads / +10 HP) but needs you to find canned apples somewhere
Choclate Factory / Bars (+25 AP, chance of addiction)
Twinkie Factory / Twinkies / Twinkie costume (Twinkies would give 0 rad / + 5 HP)
These things could only be found in ONE spot and would be sold at a premium. I got a bit frustrated that in a world where transportation in non-extistant you can find most things on any merchant.
Ranom Items:
Park Ranger Hat and Uniform
Biker Jackets (we need one that has teh sleeve cut off too

Elmer Fudd style hat/clothes ( I could've said 1950s hunting gear but this provides a much clearer picture)
Hair:
Circus Moustache
Better relation between haircuts and the bandanna
Something between the 'Rough Beard' and 'Survivalist' cuts.
Kung fu master goatee (one of those really long asian ones)
More hairstyles: Curly, afro etc
Other:
Chance to become a super mutant / ghoul with all the pros and cons. You could become a vampire in Oblivion which added alot of new and interesting gameplay chances.
I think it's simply a factor of radiation, instead of radiation leading from various forms of sickness to death it should cause those sicknesses but instead of death you reach a state of supermutanthood. (just a thought)
Playable instruments, possibly even for cash as an option with some or all NPCs. To keep this simple there could be just a handful of recorded songs per instument. Some instruments could be:Barbed Wire Banjo, Ancient Guitar, Home made Violin, and harmonica. (This wouldn't be hard at all for them to include, just provide an animation for the playing + the possiblities of gaining caps for the performance, the song would just be pre-recorded) It'd be fun! There could be another possiblity with this You could just carry around a portable record player and play records for people (guarantee this would get you caps in the fallout univers, people have always loved music).
This could open up a whole world of side quests: Finding a record player, or even finding parts of it in different locations then putting it together and also finding vinyls.
Falcon as a companion.
Innate increases perception by + 2, has a small attack vs enemies.
More Unique merchants. One part of the world is limited in say .556 ammo but you can find loads of it somewhere else. etc
Throwable darts on a dart board (in a casino or bar) for caps ofc!
Bedroll: Item stowed in your inventory. You can lay it on any flat surface and catch some Zs but you don't get the 'Well Rested' Status from it.
More skin options: you can have old / weathered skin, scabbed skin (like in The Pitt)
3 different body meshes: Strong, normal, slim. These would be determined by your strength, so 8-10 strengh gives you the 'Strong' body look, 5-7 gives you normal, and below 5 gives you slim look.
Some form of Poker.
Bet on Unarmed fights in unsavory bars or even join in.
EDIT:
Forgot creatures:
Radrantual
Raddalsnake
Tommyknockers (in mines)
Thats all!