An umbrella and a plastic poncho may come in handy in the “rainy season”.
Ear Plugs might be of help to light sleepers because Barcelona is a noisy city. There are people on the streets in the early morning hours largely due to the fact that city’s nightlife starts and finishes late for locals (and tourists alike).
To obtain Euros in advance is useful for paying for small items, gifts and food with cash, if desired.
Medical supplies and all prescription medications are a must-bring during the stay in Barcelona no matter there are plenty of drug’s stores all over the city. Spain does not do international shipment of medication that much.
A pair of sunglasses, sunscreen, after-sun cream and hat should be always in hand no matter it comes to a walk around the city or sunbathing on the beach. The sun of Spain is very heavy, especially in summer months.
A good and comfortable handbag for all necessary belongings and documents is a must. It must always be held in front because of the numerous pickpockets everywhere, especially in tourist spots and on the metro.