The Buck 119 or the KaBar would be my vote. Probably the KaBar if you want something for chopping since it has a good bit more heft to it than the Buck 119 in my opinion. The only thing I would say to consider is how large his hands are, because I remember I got my KaBar a few years later than my Buck 119 when I was 12-14 and the handle still felt quite hefty in my hand. I mean, it felt secure, like if it would slip it would just stay in my hand but on a lower part of the blade, but it always felt clumsy to actually use for some of the more precise cutting tasks than the Buck 119 was, but the 119 has more of a "countoured" ergonomic handle to it. On the one hand though, if his hand doesn't fit a 119, he won't like it at all, versus having to grow into a KaBar.
I can't really imagine chopping with the Buck 119 very effectively though, so I would say to get the KaBar Fighting/Utility knife. 7", 1095, black oxide on the blade so it will be easy for him to take care of, and you can get it in leather and teach him something about caring for that so he can have a knife with character later on, or just get one of the "black" models with the kraton handles. I personally liked the leather sheath with the stacked leather handle, but the kraton ones are nice too. On top of that you can get a Kydex sheath or a combo edge. Most of them run more in the $60-$65 range though, whereas you can get a Buck 119 for very cheap at WalMart. I think the last I heard someone say was $40.
I don't think you can really go wrong with either of those knives.
