More bills than currencies, but given the hyperinflation they relate to …
Meeses in Snow Crash. Worth one trillion dollars, backed by what’s left of the US government. Sure, most people prefer Gippers (1 quadrillion US$) bills, but the idea of Ed Meese being considered “respectable” enough to be on a US bill is amazing.
And don’t get me started on Kongbucks. Although if you have enough, I understand a fella could have a pretty good weekend In Vegas with with those.
Like in The Moon Moth? That’s not currency, though. More like people thrust valuable articles upon you because they’re thrilled you would deign to be seen wearing or using them. It happens for real, too, as you observe.
Meh. There is a picture of a real-life 10[sup]20[/sup] Hungarian pengo banknote on Wikipedia.
The post scarcity society of Cory Doctrow’s “Down and out in the Magic Kingdom” uses “Whuffie” which is essentially social standing. Positive interaction or reputation gives you more, negative less. At one point the protagonist is so poorly thought of that elevators and automatic doors stop working for him.
Harry Potter’s currency has no clear buying power or value, either.
He wins 1,000 galleons in the Triwizard tournament. He gives them to Fred and George to:
buy premises and supplies to open a store on Diagon Alley(they do this in about a year’s time)
buy Ron new dress robes(small purchase, but still)
So, how much is 1,000 galleons in USD or Pounds? I believe galleons and other currency levels are thrown about that indicate it is not $100,000 or anything like that. No idea what it is worth.
You think people who can turn lead into gold have foreign exchange and futures markets? 
It’s magic.
IIRC, in the book, the humans couldn’t even figure out how to run a bank; the industry was run by goblins and gnomes.
The ‘Black Mirror’ episode ‘Nosedive’ took this concept to its logical extreme. Someone who behaves like a dick will gradually lose all their privileges.
What?
You would standardize the size of the coins so that the denominations made sense.
Yeah, they represent favors, but the characters treat them like lending you a dollar for the vending machine is an equal favor to killing an entire rival gang.
If I owe you one, I’m going to think it’s unreasonable for you to ask me to something way out of proportion and I won’t feel bad declining. That’s why the coins in John Wick don’t make sense, they make the trivial and grandiose equal. If there was a minimum bar for a “gold coin favor” then it would make more sense.
My fanwank is that the goblins have a monopoly on coining gold into galleons, in such a magical manner that they can’t be debased, counterfeited (for very long), or otherwise magically manipulated. Goblin coinage is about the only completely trustworthy medium of exchange in the wizarding world. Not to mention the infamous security of their storage vaults.
No, it’s just that Harry Potter wizards are min-maxing munchkins who put all of their points in spellcasting, making them utterly useless at anything else.
Not fictional but certainly unusual: the wooden money of Tenino, Washington.
Sim City Buildit. Simoleons=coins you earn all day if you’re not stupid. Greenbacks=rare money you earn about 7 greenbacks a day, it can be bought with any real currency. Neo Bucks=dopey money only related to pretentious Omega-building fetishists. Purple Warbucks=money you need to play a war successfully but impossible to earn unless you play the wars or have dad’s credit card.
Eesh. Evony with a SimCity skin.
In the post-apocalyptic sports movie The Blood of Heroes, the currency appears to be small gears and other random machine parts that presumably are the remnants of the now-destroyed civilization and not expected to be produced again. It is never commented on in the film.
They’re completely unforgeable, for one–being alien artifacts rather beyond the degraded technological level that the humans are at.
That said, the book(s) are pirate stories set in the future. Quoins are just pieces of eight or doubloons or whatever piratical currency you wish to compare to. They have a physical nature, like gold coins, that is distinct from paper or electronic currency. They lend themselves to hoarding and hiding.