The Negroni is an old classic, dating back to the early 1900s, when a Count Negroni in Florence asked for an Americano (sweet Vermouth and Campari topped with club soda) with gin substituting for the soda.
Despite the simplicity of the recipe it's a difficult drink to get just right as the taste can vary wildly depending on the type of gin and vermouth used. But when it comes together it is the perfect apéritif.
1 part Campari
1 part sweet Vermouth
1 part Gin
Pour over ice, stir, and garnish with an orange peel (though I prefer a slice as you can eat the orange when you finish the drink).