When I was on the Amalfi Coast this summer I had a cocktail of which I was suspicious because it had a base of Pallini Limoncello. A 26% alcohol liqueur does not a great cocktail base make.
But the inventor of the drink, Philip Duff, made it work. He added the bitterness of tonic water and of Angostura bitters, and the acids from citrus. Together they counteract the sweetness of the limoncello enough to make a hearty yet low-alcohol cocktail.
He called the drink the LLB, named after the Lemon, Lime, and Bitters drink you find in the Caribbean.
I wrote the drink up for a post on FineCooking.com, so head over there to find the recipe.