I hadn't thought of this cocktail for a few years, until we put (rather quickly) the menu for Cobaya Gras together. The traditional version has Pimm's, 7-Up, (soda), lemon/lime, and a cucumber garnish. It was a great summertime cocktail in New Orleans among my circle of friends for a couple of summers. It's refreshing lightness keeps you going steady while not getting you completely hammered on a hot day (should you wish to marathon drink without having to annoyingly alternate your alcohol swashing with cups of water).
Napoleon House in the French Quarter has a reputation for PC's (or should that be abbreviated P'sCs?) Admittedly, the cucumber element is what first drew me into it... but the balance is what makes me remember it now.
I'm throwing it out there as an alternative to the usual round-up of 'in the sun' beverages because it doesn't seem to be known much outside of the Crescent City. And afterall, today is Mardi Gras. I think I'm going to have another one right now.
Our altered version: Pimm's, ice, cucumber lemon soda (sugar water mixed with cucumber and lemon juice fizzed in a soda siphon), cilantro sprigs. In addition to being a nice added flavor, the cilantro acts in a double role as an aromatic... similar to the function of a bouquet of mint in a julep giving a nice scent every time the glass is lifted to drink.