iTunes cards, Starbucks gift card, Target gift card. If he has a car, you could get him stuff to put in his glove compartment for an emergency like a small flashlight and tire pressure gauge or you can make up your own gift certificate for "one full tank of gas" when he's home during the winter break. You can't go wrong with a sweatshirt (hoodie) or long sleeved tshirts. If he goes to school in the Northeast, a knit hat is good seeing how guys always tend to lose them. Gift certificate to the local pizza parlor or movie theater for when he's home during the break.