Nothing could be simpler, gin and bitters. It may not be a drink I'd recommend to somebody just getting interested in cocktails, but once you've grown accustomed to the normal lineup, it's a great drink to try. The amount of bitters can easily be adjusted either up or down depending on your tastes.
1 1/2 oz gin
3 or more dashes Angostura Aromatic Bitters
Stir with ice.
Strain into cocktail glass.