Kitchenwares and food souvenirs
Go for high quality canned goods. fish/seafood, stuffed peppers, ...
You could go for cheese (hard-cheese), have a look at the Formatgeria la Seu (google-map it), it is owned by an english woman, but sells spanish cheeses; they don't vacuum pack, so the risk will be yours when going thru custom.
Below is an earlier thread on cookware stores in Barcelona. Nothing specific but you can browse the stores to get some ideas.
For food: start by browsing various mercat (La Boqueria and Santa Caterina in the old quarter are convenient for visitors) and the big food emporium, Colmado Quilez on the corner of c/Arago and Rambla de Catalunya. It has a large selection and good prices. La Ribera does have great price for saffron and the nearby Gispert is fun to browse. The food department of the El Corte Ingles facing Placa de Catalunya is good for last time souvenirs.
Most often, I bring back canned seafood. Various pastelerias have traditional Catalan cookies that are good to take back.