Teens can be diificult because they are so opinionated but they can be reaaly easy for the same reason. With a little digging you can find out what they really like and get creative with it. Is the teen a softball player? How about a personalized pouch to go in her bag that contains miniature hygeine items and some cute hair accessories? A theater kid? How about a gold necklace with the comedy/tragedy masks (you could even really wow her by finding one that includes that less common third mask, which features a more frightening face)? A glamor girl? Why not some luxury makeup or beauty supplies (a Mary Kay consultant can put together something beautiful at any price point)? Or is that boy a book lover? Get crafty by cutting up wrapping paper tubes and gluing them together in the shape of a bookshelf then buying several small gift cards to a bookdealer. Usually they are available in as little as $5 and have many designs. Get one that has the appearance of many different sections of the store such as mystery, travel, fiction, biography etc, wrap them individually and place them on your "bookshelf".
Teens can be really difficult but with some understanding of the individual (your teen years are all about being "who you are") and some creativity, you can absolutely find a gift that will thrill them.