What is the most widely misused over the counter otc medication is cough cold medication?

Very true.  
Pharmacies usually give people the opportunity to buy medicine over the counter so that they can easily treat themselves of mild ailments that might not require the intervention of a medical doctor, however, people misuse them and especially the cough cold medication. For exampe, It is a known fact that people have been found to abuse the particular cough syrup called codeine.