My favorite cocktail at the moment is a take on the Mint Julep:
2oz dark rum
cube of sugar
Lightly muddle the mint and sugar in the bottom of a whiskey glass with a small amount of rum. Add ice and the rest of the rum. Stir and serve with a mint leaf garnish.
(Why aren't there more mint flavored liquors out there? A personal quest of mine has been to discover a taste that virtually every person enjoys. Banana? Nope. Coconut? Nah. Mint? It's possible! Somebody get on it.)