For those travelling to Cuba, know that there are many things that are not available even if they are the lucky few who have received cash from a tourist.
People most often request vitamins, analgesics (aspirin, tylenol), topical skin ointments. When you give cash for services (tips) it stays in the hands of a few and those few have positioned themselves within the tourist trade for personal gain. I suggest bringing school supplies to schools, medicines to clinics, books to libraries. When you do make friends with people in Cuba, they love clothes..and they look WAY better in tiny tank tops or hot muscle shirts than American style t-shirts.