1) Olive Oil

Spanish olive oil is the best in the world (despite what the Italians and Greeks say) and Jaen in Andalusia makes half of all that is made in Andalusia, a third of all of Spain's oil and a tenth of that consumed in the entire world. It might be a little difficult to carry large quantities home - either buy a small ornamental bottle as in the picture (and refill it constantly with Spanish oil bought at home) or fill every last space in your luggage before you leave Spain with some larger bottles. Every grocery store in Spain stocks an impressive selection of olive oils.