A gin rickey combines lime juice, gin and club soda. I got my recipe from Grub Street as discovered by my wife. The writers, Rob Patronite and Robin Raisfield, suggest an unusual approach: squeeze half a lime, then slice up the spent half and muddle it in with the rest of the drink. It's a bit fussy for my tastes but on the other hand, the result is quite pulpy, which I like. Overall, it made for a refreshing, summery drink.
For more about rickeys, read here.