My sons are 18 and 21 - both would not appreciate a Barney *anything* (unless they could fill it with fireworks.) I do like the fun ideas Wrenn has listed, but trust me, the 'big three' (Barney, Pokemon, Teletubbies) are NOT the way to a young man's heart, UNLESS he specifically just happens to collect them, OR you can stand watching them 'neutralize the enemy (your gift)' in various inventive and destructive ways. hehehe ;)
Now, if he really likes something like 60's 'B' movies or was into DragonBall or DZ or Transformers or whatever, finding a big ol' Godzilla or Optimus Prime might go over well. IOW, tailor the gift to the *person*, not the age or the sex.
Basically, what does *he* like? My sons are night and day, what one would like, the other most probably wouldn't (except for certain computer games and black cargo pants.) Find what he enjoys or what he needs, then let your imagination go from there. People will treasure for years a 5 dollar gift that shows that you really know and care about *them* much more than they'll care about a generic "the salesman says this is a top saler" 50 dollar package.