I was cruising Chowhound.com, where someone else had asked a question of what to do with black radishes. Amateur chefs all over the eastern seaboard offered many very sophisticated recipes and techniques. But one commenter, whose Boston accent was so thick I could hear it through the interwebz, got it right in like two sentences. Grate the radish, add green onion and a little olive oil (and salt&pepper), and eat it with crackers and beer. Done!
Actually, I also added a splash of red wine vinegar. And the next time I made it, I added black sesame seeds because they look cool. We ate these with tortilla chips and the requisite beer.