The strangest concoction that I had was cola and hefeweisen (wheat beer). It was strange, because it was in Germany that I had it and I figured beer was sacrosanct there.
However, I learned that wheat beer doesn't have to live by the purity laws... and so Germans could feel free to mess around with their hefeweisen without becoming social outcasts.
It's called either a Colaweisen or a Diesel in different parts of Germany and it's surprisingly delicious.