1/2 shot Bailey's Irish Cream
1/2 shot Kahlua (or Tia Maria)
Half fill a shot glass with Kahlua. Hold a teaspoon over the shot glass and pour the Baileys over the back of the spoon. Et voila - a small shot that looks like a teeny-tiny Guinness. Well, not really, but they taste damn nice.
The joy of this drink is that it's not made with real alcohol, so any shandy-lifting pansy can enjoy it. Be warned though - it can result in the same degree of Carpet Mouth as real Guinness the next morning.