I love Caipirinhas especially during the warm summer months. But my favorite summer drink is still, my reining champ, the Cadillac Margarita:

Blanco or silver tequila
Fresh squeezed lime juice
Superfine sugar (to ease the tartness, usually a tsp)
Ice in a mixer (usually about three ice cubes for the size glass I use.)
Grand Marnier poured on top

Writing this just ignited my desire for one! Why not, it is summer!