That's why I'm not a big fan of Metro's currency, it's weird to have 'money' that's also often consumed in game through other actions besides buying things. It creates a weird economy.

... as opposed to having money you spend on bullets which are then consumed in game?

Yes. Money that I can spend on bullets or other gear or whatever. Money that is, as money should be, an abstract concept of value.

Creating a currency that also has a primary function in the game's combat feels bad to me. You essentially force the player to bankrupt themselves in order to stay alive. You end up creating moments when the player regrets doing the ONE THING you've created the game for them to do, kill things. Shooting your gun is negatively reinforced by directly costing the player money. In other games if I get a crap load of ammo I can go nuts with it, go rambo, fuck things up without so much as an inkling of a strategy and just enjoy the mechanics of the weapon. Knowing that even after I waste some ammo it's not going to stop me from using my other money and that my other weapons have enough ammo to sort me out for the foresee-able future.

The concession I'll make is that if your goal is to make the person into a serious gear-miser and constantly worry about their inventory, then I'd take the Metro method. However I still think there are better ways to do this.

Lastly though, if you stick with the Metro method, you box yourself in economy-wise. I can't see a way of having an actual dynamic economy when the player can dump half a town's GDP into a wall inside of a minute. Additionally, you'll run into complications regarding ammo drops around conflict areas and boss room balancing. There's a lot you could do to solve for those issues, but doesn't seem worth it to me.

I have to agree with Eaglerufio, I also don't like the ammo IS money option. It just doesnt feel nice for me as a player.

I also hated the barter system of Path of Exile. It made it impossible to quickly know the value of different loot and clogged the inventory.

I might go with small batteries, or gold nuggets, or whatever.

If i go with a world with a brutal government which controls cities and rebels hiding in the wilderness, things like batteries will still be produced (since there are evil robots and hitech weapons) however so it might not work as currency.

But the thread was more about how the world would work around having money AT ALL. Not what thing is used to represent it.

If its ALL humans VS some evil force i think it would be strange. Everyone would just help in the way they could. But if lines are blurred, some are "neutral" to the two sides you will maybe have a more or less standarized currency.

I think you are looking for something that is not consumable so that the money is just money and can only be used to buy things and not eaten or shot etc..

So

Scenario 1. You already said their are settlements with their own economy. I don't think they'd use paper money as each settlement would potentially have a separate currency. Probably precious metals or gem stones would be a good candidate and also redilly available as the population would be smaller so things like jewellery, silverware, old catalytic converters would be much more abundant per person. Or you could go the wacky route and have something like fallouts bottle caps. I think in the case of a Zombie apocalypse then something like dried zombie fingers would work.

Scenario 2. This one is much simpler. The evil corporation would most likely have some kind of currency system (paper money, credit chips, coins). Even if you are the resistance you would still need to use the global currency to buy things.

In the event of a zombie apocalypse, the survival of paper money seems highly unlikely. The coins that supplement the paper money, though, seems a lot more durable. Coins like pennies, nickels, dimes, quarters are common in North America, and would still be common enough to exist after your average apocalypse, even if there's no continuing production.

Additionally, it's a "new" currency system, so you're not necessarily bound to 1 nickel = 5 pennies, etc. Different coins could have higher value in certain settlements (Clan A really likes dimes, so it'll take 8 dimes to buy bread instead of 10 nickels), or certain settlements could each have their own "currency" (settlement B accepts only pennies, settlement C accepts only quarters).

If you set it in Canada, you have two more coins to work with! :D ( 1$ loonies and 2$ toonies)

I think it can be fun to have no official currency and having to find out what each NPC values without saying too much about yourself (which can call an ambush).

If universal currency is prefered then I would say some long lasting food (beans, dried lizards etc.) and gasoline which represents mobility, heat source or can be a weapon...

In all honesty a system of currency implies civilisation and possibly government. The first money systems appeared with the first big civilisations and monarchies/governments/republics such as ancient Greece and the Roman Empire.

Without a central mint to produce currency and a government to regulate it and ensure it maintains value and has a CONSISTENT value across geographic distance it would cease to have any relevance.What would be the point if you had to pay $30 for ammo in town A when town B sold it for half the price just 10 miles away?

Any realistic game should probably only use a barter system, but this is hard to do well and gameplay should be more important than realism IMHO.

In theory, arbitrage should smooth out gradients. If neighboring towns end up with ammo prices diverging too much, somebody would eventually buy the ammo in A and sell it in B. Now, if town C is 50 miles through the mountains, it could maintain a very high cost of ammo. This could even be a source of gameplay for the players, suffering risks in return for profit.

I agree that money developed in relatively sophisticated circumstances, but it's not clear whether that's a necessity to maintain a currency system once one exists. I suspect people who had been part of a stable civilization would miss the usefulness of fungible money and be eager to recreate it if possible.

Partially it's a trust issue: do you think someone else will take this currency for what you really want? If the issue is a zombie breakdown or whatever, the basic fabric of trust that weaves a society together isn't necessarily torn to bits. If everyone standardizes on "zombie fingers are money" and "around here, approximately 10 zombie hands to the gallon of gas", then that could be enough to keep a monetary system going.

Any realistic game should probably only use a barter system, but this is hard to do well and gameplay should be more important than realism IMHO.

In any barter system there usually ends up being one commodity that is in demand so much that it becomes the default currency. Historically it has been things like cows, camels, rice, salt etc..
The barter system would certainly happen but in the OPs example society has already started to kickstart itself again so I can imagine that some unit of currency would already be the de-facto item that is used to barter with. I think Revynes example of razor blades and Bic lighters is a more modern example of commodities that could be in demand as the new currency. However his example seems more like a survival situation rather than something long term.