You tend to think of Nerdcore rappers as having come out of the world of geek culture and then getting into rap — rather than starting out in hip hop and then starting to rap about nerdy stuff. But Richie Branson (aka Marcus Brown) started out producing rap albums for Def Jam and Sony — and then he decided to get into nerdcore. He's created downloadable mix tapes about Star Wars: The Old Republic (called "The Cold Republic") and Gundam Wing (called "Wing Zero Mixtape") and you can listen to one of his Gundam songs above.
Branson tells My San Antonio that he tried rapping about cars or girls, but it wasn't until he was playing The Old Republic and took a bathroom break while listening to the video game music that he hit on his subject matter. After that, he says, "I finally had found my identity as a musician."