You'll definitely need limes for several mixed drinks and some beers! Anything mixed with club soda, sour mix, coke, or cranberry can use a lime to brighten the flavor.
Lemons are used sparingly. They can be added to a drink when lemon juice is used, but are typically used for decoration more than flavor.
Herbs add fragrance to your drink. Mint can be muddled in or used on top to add a light freshness. Rosemary compliments drinks with fruit or floral flavors. Cinnamon sticks add warmth to a cider, which is great for the winter.
Cocktail olives or onions can be added to martinis for a savory flavor. Meanwhile, cherries are added to otherwise plain looking, bitter drinks for sweetness and a pop of color.