Assuming he has all of the run of the mill stuff like jerseys, tshirts, hats, etc. you might try getting him a 1996-97 Topps Chrome Kobe Bryant Rookie Card. They go for about $300 on ebay but that's considered his best "rookie card" and that would be cool. Also might consider getting him a signed jersey or signed basketball card. You know you are buying authentic signed cards when you buy from major companies like upper deck, fleer, etc.