Fun thread idea. Mine is definitely the 1958 Menko Doyusha JCM30a Jackie Robinson card. It's my holy grail card, and one that I was fortunate to have been able to track down earlier this year on my birthday. My copy is shown below.
Why do I like it?
For one, I just love the look of the card. It's sized like a T card, but has the color and pop feel of an Andy Warhol art piece. It has a very bright and bold almost neon magenta background to it. I love the back as well. Just a classic piece of art overall. It's a stunning card in hand.
In addition to how it looks, it's also a really cool historical piece. Throughout the entirety of Jackie's career, there was enormous tension between the US and Japan in the wake of the Pearl Harbor attack and our retaliations in Hiroshima and Nagasaki. But what most fans don't know is that in 1956, after the conclusion of the World Series, Jackie and the Brooklyn Dodgers (sans Koufax) traveled to Japan to play a 19-game exhibition series against Japanese players and teams in an effort to bring the two nations closer together and forge bonds of peace. They were invited by Matsutaro Shoriki, the "father of Japanese baseball", who was the man responsible for Babe Ruth's famous Japanese tour in 1934. 1956 was also the year that Jackie Robinson retired. His final game in a Dodgers uniform was played in this series, on Tokyo soil, and his last hit was a HR that erupted the crowd.
Cool story, but why he has a Japanese Menko card is a bit of a mystery. The Kanji on this card reads, "Roberto Chico Barbon". At the time this card was produced, in 1958, Barbon was the only black player in Japanese baseball, and as indicated on the card, he wore #8 for the Hankyu Braves. But instead of picturing Barbon, the card features Jackie Robinson. It is assumed to be an error card that was likely pulled from production, although an actual "Chico" Barbon replacement card was never made.
It is by far Jackie's rarest card, as there are only 5 copies known to exist: 4 on the PSA pop report, and 1 on SGC. Perhaps there are more that will surface in the future though, as they command steep prices whenever one hits the market.
Sean, from Victory Investments, made a great documentary about this card last year. It's worth checking out if you're interested:
https://youtu.be/VBDvF_dD5BU