This is one I hadn't seen posted yet, so I figured I'd get us started. FNV has a reputation system, FO3 does not, but the factions in FO3 are perfect for the Rep system.
I'll start out by showing the Major and Minor factions in each game (I used the Wiki to help, so if I have missed any please let me know.)
Mojave Wasteland - Major Factions:
Brotherhood of Steel
Mojave Wasteland - Minor Factions:
Followers of Apocalypse
There are other sub-factions, but I have only listed the ones with Reputation assigned to them, according to the Wiki. Following a similar format to the one above, here are the CW factions. Whether or not they should be assigned reputation is the point of this discussion.
Capital Wasteland - Major Factions:
Brotherhood of Steel
Capital Wasteland - Minor Factions:
Canterbury Commons (not listed on the Wiki, I added this one)
Other minor CW factions:
Republic of Dave (might need to move this one up)
Reilly's Rangers (might need to move this one up)
Underworld (might need to move this one up, not listed on the Wiki, I added this one)
Little Lamplight (might need to move this one up, not listed on the Wiki, I added this one)
Andale (not listed in the Wiki, I added this one)
Littlehorn and Associates
Rivet City (Wiki lists RC Council and RC Security as separate factions, might need to move this one up)
Vault 101 (might need to move this one up)
CW DLC Factions:
CW Religions (Don't know if these should be included in rep or not):
Apostles of the Holy Light
Church of the Children of Atom
Point Lookout Tribals
Saint Monica's Church
That's it for the breakdown of factions. I'll update and edit the OP here with more info as the discussion progresses.
I guess the major questions are:
1) Is it possible to add reputations to the FO3 factions?
2) Should we even bother adding reputation to the FO3 factions, or just wait to have rep until the player reaches the MW?
3) How do we deal with factions like the Brotherhood of Steel, which exist in both the CW and MW?
4) How would certain quests or objectives change FO3 reputations?
5) Should the various religions be included in the reputation system?
6) Which factions/sub-factions should be given reputation and which should be left out, and why?
7) What should the effects of reputation be? (bonuses for Accepted/Liked/Idolized, penalties for Shunned/Hated/Vilified)