It depends on what he likes ultimately. If he is kind of "outdoor & adventurous" the it would be backpack, GPS, trekking boots etc. If he is some one who likes music, then an IPod, If he likes reading then an amazon kindle, for someone into office and business all the time, it would be a blackberry mobile, if he is a student then a laptop computer, and so on.
The common thing in all this, most young men like electronic gadgets in whatever they are interested in. This could give you a clue.
If your guy likes gaming, probably a PS3 would be an ideal gift. Refer my hub https://hubpages.com/holidays/Why-PS3-Makes-for-a-... to know why. Thanks.