triple sec
Basically triple sec is an orange liqueur, therefore in my opinion, it is a must in every home bar. Although the word sec means dry in French, triple sec does not mean triple dry. In fact it has to do more with how many times the liquor has been distilled.
Other orange liqueurs are: Grand Marnier, and Cointreau. Both of these are more expensive, and high brow than their lowly cousin triple sec. Nevertheless, they both serve their purpose.
Triple sec is widely used in margaritas for example. My blue margarita comes to mind.
Grand Marnier, and Cointreau are more for sipping.