A cherry garnish is classic. Nothing embellishes a Pre-prohibition Martini or an Old Fashioned quite like a cherry. But this comes with a major caveat: the run of the mill electric-red maraschino cherry that you find in the supermarket is not only full of nasty chemicals, but, in our opinion does nothing to improve the flavour of a fine cocktail.
There are a host of other amazing options, however, including brandied cherries like Griottines and Luxardo Maraschino cherries. You can find them at specialty food shops. Treat yourself!