just read a cool article about infusing flavors into oysters the "natural" way. They dunked the oysters into pickle juice for about 3 hours and let the little filter feeders "feed" on the brine. The result was an oyster with a hint of pickle. I'm not sure why they couldn't just add a drop of pickle juice onto a freshly shuck one, but it sure was a neat idea that took advantage of what oysters do best.
I like mine straight up with a dash of lemon. I was at a fancy raw bar that had freshly grated horseradish, that was good stuff, but not often readily available.