#1 A WW1 western front trench roleplay. Users would play a character that could be from either side, representing British and German soldiers during periods of combat and ceasefire, mainly during the Christmas Truce. The soldiers would bond with each other then get to know their enemies during the truce, make trade with champagne and chocolates etc, play football (soccer) and then return back to fighting the next day.
And I thought of an idea to make it more warlike, after a certain period of time, combat would resume along the front, every character would be issued a number from one to, how many characters there happen to be, and I would roll a dice, so if there were seven soldiers in total I would roll a 1d7 and whoever's number came up that character would be killed in action. Of course the user wouldn't be kicked out of the roleplay rather they would create a new character that would represent fresh reinforcements from the support lines.

#2 A roleplay set in the Fallout universe, mainly Fallout 1, I'm sure we've all played at least one of the games, otherwise a quick summary can be found here.
There's a couple Fallout RP's hovering around every now and then, but most of them all focus on Fallout 3 and have their unrelated characters already out in the wasteland already experiencing everything.
My idea is that everyone is a member of the Vault 13, instead of one character being chosen by the overseer of the vault to find the water chip; rather a whole group is chosen. Users would play one of the characters in this group. Set forth as a team in a dangerous, post-apocalyptic land they know nothing about (locations could be canon or not), would they work together or go their own ways.

Personally I don't like idea #1, since you are quite limited in your actions. It might be interesting since it's deals with war on the most horrid side, but I don't think that will last for very long. It is missing a plot. The idea of death being close is good though, something that isn't present in most RPGs here.

Idea #2 however, undoubtedly boosted since I'm a fan of the fallout series (especially the first two parts), I like a lot. It brings a plot and a large world into view. Although it might be better if the world got discarded, or we'll immediately end up in shady sands killing rad-scorpions.

The characters start with little resources and no knowledge of the world, which is rather unforgiving. They would however know each other, since they were all in the same vault, so their histories would have to be tuned towards each other. Should all be very interesting, but would require more effort at character creation, then again your history is restricted to the vault.

Hmm, well you're right about actions being limited, that's why I thought it would be more of a character interaction, not action based roleplay. Seeing how the soldiers deal with death, friendship, boredom, pondering philosophical views etc.

As for discarding the world in #2, yeah I could definetly see how that would benefit, I immediatley got Shady Sands as the first stop in my mind when thinking of this too. So who would think up all the places there are to visit, the GM, or the users as well? No knowledge of the world just leads to more creativity and suprise I would think.
Also the vaults are quite large so the characters don't neccesarily have to know each other very well, and there's plenty of things they can do in the vault, to somewhat flesh out their history.