If you've seen an episode of Justice League or Ben 10, you've seen his work. He was a brilliant writer.
A native of Detroit, McDuffie officially joined the comics industry as part of Marvel Comics editorial in the late '80s. While working on special projects for the publisher, he quickly made his name as a writer creating series such as "Damage Control" and helping to redefine the Deathlok character to fan and critical acclaim. He soon left the staff to become a full time freelance writer, becoming a voice in the industry for diversity, particularly fighting against stereotypical portrayals of people of color on the comic book page.
In 1993, McDuffie co-founded Milestone Media along with creators Denys Cowan, Michael Davis and Derek T. Dingle. The company's mission statement involved expanding the role of minorities in comics both on the page and off, and they launched (through DC Comics) a line of superheroes that included "Static," "Icon" and Xombi" – all of which McDuffie had a hand in creating.
Maddy from When Fangirls Attack has a comprehensive list of links about McDuffie's passing. Check it out.