Which ingredient is unique to the Rum Runner cocktail?

The inclusion of Creme de Banana in the Rum Runner cocktail is what makes it unique among the typical ingredients found in other cocktails. This liqueur brings a distinct banana flavor that complements the other fruit flavors in the drink, such as raspberry and orange, creating a sweet and fruity profile. The combination of rum with this particular liqueur is a defining characteristic of the Rum Runner, setting it apart from other cocktails that do not use banana liqueur.

The other ingredients, while they may be used in various cocktails, do not have the same signature association with the Rum Runner. Cranberry juice, for example, is a common mixer in many drinks, as are liqueurs like Frangelico and Pernod. However, Creme de Banana is central to the Rum Runner's unique taste and experience, solidifying its role as a key ingredient.