Butterbeer cork necklace

Luna Lovegood, a Ravenclaw student, has a Butterbeer cork necklace that she wears. Everyone finds it particulary weird. She also has a pair of Radish earrings.

Behind the scenes
In Harry Potter and the Order of the Phoenix (film), Evanna Lynch wears a Butterbeer cork necklace with just one cork on it. She claims it keeps away the Nargles.