I like this citrus-y drink, particularly over ice. It's called “potion of power” after Rachel's assertion that unsweetened grapefruit juice and unsweetened cranberry juice both taste like battery acid. If you use relatively sweet orange juice, this is good unsweetened. Otherwise, I'd add a pinch of sugar, substitute some Sprite for the seltzer, or substitute CranApple for the cranberry juice.
I'd guess that an alcoholic version of this drink would be tasty, particularly if you made it a little sweeter. I'm not really into mixed drinks, but if you make one out of this and it's good, please tell me.