well buy them some season tickets to some sporting events or something, like buy pair of tickets to the most difficult game to get and you would be how surprise they will be afterwards. if not then probably go out to a nice place and eat or something like that.
Try getting him an "adventure gift," like tickets to a ball game, sporting equipment, reservations to his favorite restaurant, or something else that he can do.
The best thing you can do is to look for hints of things he wants around his birthday. He will love that you paid attention to what he said. Personalized gifts are wonderful too for guys.