Germans have picked up on all styles of American pop music, it seems, including rap. It sounds very strange at first, but, if you're learning the language, you can become accustomed to it, even if you don't like the genre, although it still sounds strange to me when they say nigga, a word surely imported on the rap boat. One of the most popular German rap groups is the Fantastischen Vier (Fantastic Four) featuring Thomas D.
Unlike their beer, I doubt German rap will be popular in the States anytime soon.