What citrus garnish is commonly used in a Vodka Martini?

A lemon twist is commonly used as a garnish in a Vodka Martini because it enhances the drink's crisp and refreshing profile. The oils released from the lemon peel add a bright and zesty aroma that complements the clean, neutral flavor of vodka. This combination elevates the overall drinking experience, providing both visual appeal and a hint of citrus essence without overwhelming the cocktail.

While other garnishes, such as an orange peel or a cherry, can be used in different cocktails, they don't align with the traditional presentation of a Vodka Martini. The use of a leek as a garnish is not common in any standard cocktail, making it an unlikely choice in this context.