These traditional Basque pickled peppers, also known as "guindillas", are amazingly versatile. A bit spicy, but really more tangy than picante, they're the perfect foil for tapas involving anchovies or tuna. That tangy quality also makes them a great addition to salads, sandwiches, even chopped up to garnish beans or accent richer rice dishes.
And of course, the classic one-bite pintxo (Basque tapa) known as the Gilda would be impossible without piparras: skewer an olive, a piparra, and an anchovy together on a toothpick, and eat them all at once. Perfection.