ZOMG - on the weekend I discovered this one:

1 x beetroot
3 x apples
1 x small lemon
1 x pinch of mint

apple-carrot-celery-ginger-orange is also a fave
watermelon-pear-beetroot is one I had with my sis once that was awesome, and always reminds me of her. We call it Barbie Juice.
grapefruit-pear-carrot
apple-strawberry-kiwi

You can use anything. When it's fresh, it all tastes amazing.