Boy, that's a toughie. I'd ask your local bike shop if they would accept returns on gifts if his bike wasn't to his liking, or if the fit and/or style was wrong. What kind of riding does he plan to do? Trails, jumps, etc? For that kind of money, you'll be limited to entry level hardtails. I have some friends who have the base model Specialized Hardrock and they're quite pleased. At his size, he'll probably need like a 19" frame or so. If you could have him test ride some bikes to give you an idea, that would be helpful. But if it's going to be a complete surprise, you might not like that option. What brands are available to you at your LBS(s)?
There's always a gift certificate.(?)
My wife and I both just bought bikes as early Christmas gifts to oursleves, but we were able to test ride a few different models within our price range and riding style before deciding.
Good luck. You should be able to find some smokin' deals on end-of-year 2005 models.
Ian
Austin, TX