Jerry Robinson, an artist on the early Batman comics, co-created both the Joker and Robin, the Boy Wonder. But he was virtually unknown outside of fan circles, since Bob Kane's contract with DC said that only his name could appear on Batman stories, a policy that went unchanged until the 60's, IIRC. He died on Dec. 7.
One week later, on December 14, Joe Simon also died. Joe was better known as the co-creator, with Jack Kirby, of Captain America. He and Kirby also invented the Romance Comic genre. And in later years, as Kirby was returning to DC Comics to work on his Fourth World books, Simon was writing books like Prez and Brother Power, the Geek. It was Kirby who sucked up all the press and accolades in later years, and justly so, given Kirby's role in creating the Marvel Universe, but Simon should never be forgotten. The men were a team for decades.