If he is into his music you could get him an i-pod quite pricey but worth the money.
my boyfriend is the same age and for his last birthday I got him a really nice dkny watch he seemed really pleased with it.
like shineybomb said a psp but dont expect to see him much once he's got it, also nintendo has just released the new version of the DS bit cheaper than the PSP my fella works in game station and there was an offer on where u got a console and 2 games not sure how much for though he may like that if he's into his games.
clare x