Most teenage guys like music, so a pair of headphones with some good sound quality, especially if they're a souped-up pair like being washable, might make a practical and stylish gift. Young audiophiles might also appreciate a solid pair of portable, wireless Bluetooth-enabled speakers, which would enable them to play music off their smartphone, like their Windows Phone or iPhone, or their tablet.
Every guy loves t-shirts; they never go out of style, which makes this choice a virtual no-brainer. If the recipient has a certain band that he loves or superhero that he admires, then getting a t-shirt emblazoned with one of his favorites would be a smart decision. Similarly, a sweatshirt with his favorite sports team logo on it would make a good Christmas gift. Other clothing gift ideas include a nice hooded sweatshirt, which is practically de rigueur in some actions sports like skateboarding or if he's a young coder.
If he snaps a lot of pictures, as he probably does, then he might really go for a telephoto lens for his camera. Even if he has an iPhone or iPad, he might appreciate the optical zoom that the telephoto lens would add to his any photo equipment he might have.