I got him a collection of used (but nice/newish) shirts from thrift stores for the college he'll attend in the fall. He has used a lot of the money from his job for music for his I-pod, and I can't imagine giving him a I-tunes gift card because he has so much music. In-laws gave him a camera years ago that he rarely uses.
Yes, I have directly asked him. He says he does not want anything.
Clearly, he has everything he needs and more. But I feel the need to get him something.