it would definitely depend on his hobby..if he is a guy who likes to collect something, maybe you could try to start out with something...if he likes cars, then you can buy him small cars as a collection. Or anime toys or comic books of his fave super heroes, OR IF HE HAS A CURRENT COLLECTION - add some more....If he likes to read, find his fave author or you could scout on some good reads....if he is very very busy - no time to relax - you could also treat him to a weekend getaway...he might as well like a shirt or a pants - men seldom buy one, but if we receive something...we kinda treasure that...esp. if we like it's design and if it's comfy...

Base the gift on his interest and favorites. Something that is easy to see. Something that would definitely make him smile. More information about the receiver so that we can help.