Rumpleminze (peppermint schnapps) and coffee and cream creates a smooth and potent alcoholic drink. Add a Godiva Chocolate Liquor for a first class-after dinner cocktail.
Grand Marnier(something like an orange flavored brandy) goes well with both black coffee and coffee and cream. If you like your coffee black Grand Mariner adds flavor and potency without adding a lot of sweetness. Of course it goes just as well with cream, which results in something a lot like a chocolate orange.
A Tuaca(people often describe it as tasting something like butterscotch) Macchiatto(my own recipe) is an alchololic twist on the classic coffeeshop favorite. Mix a shot of Tuaca into a shot of steamed milk. Top with Coffee. This tastes mild but packs a decent punch, and if you take the time to do it properly ("mark it"), it looks pretty cool. (This also tastes great with regular milk or cream.)
A second variation on this, which is far less potent is to replace Tuaca with 1/2 a shot of Chambord and 1/2 a shot of Godiva White Chocolate Liqueur and mix thoroughly . This will an tasty adult white chocolate mocha.
Finally, a classic cocktail combination is coffee (with or without cream) and Sambuca. Sambuca is often served with 3 coffee beans, but it works very well with an entire cup. Sambuca contributes a lithe sweetness that delicately lingers in the mouth. Avoid if you don't like Anise or Licorice.
For a seriously potent version of Sambuca and Coffee swap out Sambuca for Absinthe(not refined). In addition to the alcohol content, Absinthe also offers a jolt akin to what caffeine provides.
Be responsible and Enjoy!