This is probably the most interesting one I have:
Victor "Young" Perez was a flyweight champ of Tunisian descent who lived in France. Come WWII, as a Jew he was betrayed to the Nazis and sent to the Auschwitz death camp in Poland where he was forced to fight gladiatorial contests for the amusement of the guards. If he won, he was fed. If he lost, he would be executed. He never lost. He was finally murdered during a death march near the end of the war when he shared some bread with a fellow prisoner in defiance of a guard's orders. Perez's cards--there are a few--are sought after because of his story. His autograph is rare for obvious reasons. Another collector and I put our heads together and were able to come up with only a few examples.
Honorable mentions:
For years I thought how cool would it be to get a signed Bowman Groucho card but who knew if one even existed. Then one morning while suffering through a bout of insomnia I came across this one on eBay, BINed and it was mine.
Favorite Jazz Age artist.