This is what comes to my mind, 1/1 pokemon cards which are basically nonexistent in tcg. Topps bought back cards (not just pokemon but whatever they had released) during their 75th anniversary celebration, stamped them and released them in special boosters. Every stamped card is the only copy in the world
Edit:
A better photo of the stamp
that disco holo goes crazy. found an auction of the sheet here with some better pics Hake's - 1999 POKÉMON UNLIMITED BASE SET HOLOGRAPHIC UNCUT PROOF SHEET WITH 100 CARDS.
Oh, I had no idea they were 1 of 1. I have saved pictures of some of those (see below), since I knew they were very rare, but I had no idea they were THAT rare! 
Greetz,
Quuador
Yeah they are, basically a topps collector’s daydreams 
i haven’t seen any pokemon stamped past series 1 so don’t have my hopes high a grimer or muk exists but one can always dream!
How do you know that they’re 1/1? 
Well i guess i don’t know for sure, have just heard several people say that and have never seen multiples of the same card, and when thinking of their rarity and the spread of all the cards stamped i had no doubts believing they are 1/1 but can’t say that for sure. But until i see a multiple of one card i’m still thinking that way 
1/1 or 1 of a handful its pretty much the same thing. Rare as hell for sure. Im yet to see an ebay listing for even 1.
This still blows my mind that it was even noticed. Kanzenban Mewtwo. It’s just something that could have easily gone unnoticed forever. Such a simple thing that could have been lost in history.
The card is nothing special or rare, the colours are so vague, the card stock is only noticeable when holding both. The VHS is rare, but not really for any special reason and it’s not really valuable. Just so many combing factors that scream this card was meant to be never given much attention. It’s possibly the greatest amount of joy this forum has brought me.
I try to pick one up every time I identify one just because it’s so ridiculously hard to locate.
Ooh lots of these look familiar 
I’m happy I could pick up some from samsamsam back when they were up on eBay. I know the other collector who scooped up the others that I didn’t purchase.
Wow that’s awesome! I hadn’t seen this one before! That makes a total of about 23 cards I am aware of!
How did he get them? Did he open a bunch of the 75th anniversary boxes?
Curious to know as well…asking for a friend… 
Thats an awesome card! The weird uniqueness to these makes me wish I could come across one even though Im sure its out of my range.
Found out about them two years ago while scrolling bulbapiedia’s Topps page.
I asked if anyone knew anything on e4 discord and I don’t remember getting any replies. I was closely monitoring eBay since.
A huge Topps collector (the one who created the original Topps thread on e4, samsamsam) used a middleman on eBay to sell his 15 cards as seen in @quuador’s photo, I purchased 3 from this lot and pokemontoppsuk bought the rest (or perhaps a selection).
Not too long afterwards a seller appeared on eBay selling 5 more cards.
I bought 4 and pokemon radar bought 1.
Since then I missed a series 1 charmeleon that was on eBay (I changed my saved searches so I wouldn’t miss it again).
I know of perhaps 5 other cards in existence that either other collectors own or their images just exist online.
I’m unsure but it could be possible two copies of “the best of the best” exist. I own one and another was in samsamsam’s eBay lot.
As well, two clefable exist; however, one is holographic and the other is not.
Thanks for the great info! Do you know if there are any Oddish cards? 
I’ve never seen an oddish or an oddish cameo you’re in the clear so far
Phew 
