Ok, here's one that I suggest you don't try at home. Someone emailed it to me and said give it a go:
1 x apple
1 x pear
1/2 a lime
I just whizzed it up and it soon seperated with a pleasant froth at the top and a very citric, sour drink at the bottom. I think maybe with it a bit of experimenting it could be a nice drink - maybe less lime or a couple of apples to balance it up a bit better. I'm still recovering from quite how sharp that was!