Which cocktail is commonly made with gin?

The Negroni is indeed a cocktail commonly made with gin. This classic Italian drink is composed of equal parts of gin, sweet vermouth, and Campari. The gin in this cocktail is essential, as it provides a strong base and distinct botanical flavors that complement the sweetness of the vermouth and the bitterness of the Campari.

While the other options do contain spirits, they do not traditionally use gin as a primary ingredient. The Martini is also a gin-based cocktail, which could lead to confusion in the selection. The Margarita is primarily made with tequila, and the Old Fashioned is based on whiskey. Thus, the Negroni stands out for its specific requirement of gin, showcasing its role as a key ingredient in this particular cocktail.