For being awake during the day, I prefer Dimetapp. You can match your symptoms to the variety of options available. For night time coughing, I use Nyquil. It really helps you sleep. You don't have to buy the name brand. The drug store knock-offs are every bit as good as the original.
I think that the best over the counter medicine for a cough is mucinex. There are different types of this medicine... make sure it is the one for a cough.
Medications for coughs are available in so many different formulations, not just brands. To determimne the best choice for you, you must ascertain which one meets your particular type of cough. Often there are store brands at much reduced prices that are equivalent to the formulation you require.
Delsym is the best cough medicine I've ever. It was recommended by my allergy doctor for acute bronchitis. It's available over the counter but you actually have to ask the pharmacist for it. (They keep behind the counter. ) The only flavor is orange (yuck! ) but it's worth it.