As a left-handed player, I use the keypad for everything (8426 for movement, 5 for activate, Enter for jump, / for reload, + for pipboy, etc.). For me, playing a game with WASD is as natural as playing with my toes and elbows...
Fallout 3 has custom key mapping except for the 'Take All = A' and 'Exit = E' functions. Seems small, but every time I loot a container (which is more common in FO3 than combat), I have to go from using hotkeys to clicking on the function, or reaching over for the A/E keys. Skyrim lets you map those functions, but FO3 does not and it's surprisingly frustrating.
I don't know how difficult it would be to make the Take All and Exit container functions custom-mappable, but I sure would love to see it. If that's too complex, than a hardcoded mod to remap Take All to keypad asterisk and Exit to keypad minus would suit me personally - though I'm sure other left-handed players would map them to other keys.
Statistically, at least a tenth of all PC gamers are left-handed - shame on developers that only allow WASD or don't allow the keypad to be re-mapped!