World Numismatics Record That's Worth Mentioning?

I have seen the one tonne gold coin in at the Perth Mint, where it is on public display.
You can walk right up to it and touch it.
It is about 1 metre in diameter, and about 4 or 5 inches thick.
It is cast, not struck.

It IS available for sale if you have enough idle fiat money lying about to purchase it!
It would have to be the World's most expensive numismatic item.
On current spot gold price, you will need about $51.4 million to buy it.

I have figured that the Tongan 1/4, 1/2 and One Hau of 1967 were the first palladium coins. That is what my copy of Krause reports.
If in fact that the 1966 Sierra Leone coins were the first, it seems to me that this issue must have been NCLT (as with the Tongan coins), but released in a range of metals which included palladium.

I remember seeing a set of the Tongan coins not long after release. They looked like cupronickel coins, however they were denominated in Hau.

World's largest round copper coin: probably Russian 1777 "Sestroretsk" 1 ruble (I might be mistaken, but IIRC everything larger than that - such as the Swedish plate money - wasn't round, and early Roman Republic coppers, while round, never got quite that big).

...Anyone has any suggestions for the least face value coin ever produced for circulation? (I'm saying "for circulation" to exclude cases like Belarus (still) making their commemoratives with a face value of 1 ruble, which would've otherwise been the least face value coin still produced today; but as mentioned below, it's still not always obvious, and then we have cases like the Yugoslav 1994 dinar when it's hard to determine the coin's value at production because the currency hyperinflated wildly).
My personal suggestion: 2009 Russian 1 copeck, at circa 0.031 US cents [as of 2009; maybe 0.035 now]. I know the Philippine 1 sentimo is still produced, at a lesser face value, but calling it "for circulation" would be optimistic (or at least it was apparently never intended to circulate).