UPDATE (July 2021): Someone has found a winning card that survived destruction!

Remember Nintendo's e-Reader?  Sure you do.  It's the card-scanning add-on for the Game Boy Advance that never really quite took off.  Special cards could be scanned through the e-Reader's slot which would then drop some new data into the GBA, be it entirely small self-contained games or additional data for GBA games (remember Super Mario Advance 4's World-e and its lost levels?).  Then there's the rare and hard to find e-Cards that were promotional in nature; cards that were nearly "proof of concept" in nature and would only put, say, a dancing Pikachu on the screen just to prove the whole gimmick worked.  Considering that the e-Cards were discontinued fairly quickly and the whole e-Reader concept was junked, Nintendo didn't produce too many e-Cards, and the cards they did produce are becoming harder to find in good shape these days.  Muddying things a bit is the fact that Japan and North America each received their own unique sets of cards.  If you're an aspiring e-Card collector, then you have quite a journey ahead of you.  You may well acquire all of the rare cards that were once sold at retail, but chances are that you'll be hard pressed to snag the rarest e-Card of them all.  Rarer than the Mario vs. Donkey Kong e-Cards, it's the E3 2002 promotional Kirby card!

E3 2002 promotional Kirby e-Reader cards were distributed on the E3 showfloor. Each card was printed in 3 variants - no prize, 2nd prize, and 1st prize. Scanning the card would result in confirmation if you've won a prize or not. All winning cards were later destroyed. pic.twitter.com/w06lyeIpNa

— Kirby: Star Facts (@FactsKirby) February 27, 2019

Printed in three different varieties (no prize, second prize, and first prize), these cards were given to attendees and scanned on the E3 show floor.  Kirby would appear on the screen after scanning the card to tell you if you'd won a prize.  Only one hundred "second prize" cards were printed while just ten "first prize" cards were created, and those who wound up with a winning card had to hand it over to Nintendo representatives to collect the prize.  The fate of winning cards was unfortunate: they were ripped apart to prevent someone from trying to redeem them a second time.  There's no telling how many of these cards still exist, but it's a good bet that if you can find one now it'll probably be a "no prize" card.  I have to wonder which is more valuable today: a winning Kirby e-Card or the prize for which the card was traded.