Cold coffee, with or without ice in it.
Simple syrup is better than sugar as a sweetener for iced coffee (or anything else cold, like iced tea), since cold liquids do not disolve sugar very well.
While you can procure this tasty and refreshing beverage at practically any coffee shop, I have not been able to find any pre-packaged renditions that do not contain some sort of milky stuff and much sweetness.
Oddly enough, $tarbucks does not sell iced coffee, at least not in my bit of the world. They will make you an iced Americano (espresso + water), but it's just not the same.
You will occasionally find blended drinks
being called iced coffee (e.g. espresso
+ ice + milk + sugar, run through the ol' Osterizer
); some include alcohol
or other flavorings. However, "true" iced coffee is just cold coffee.