A Ka-Bar would be a very cool present, couple howevers though:
- Some Marine units (most that I've been in) won't let enlisted men keep knives over a certain length in the barracks, and that does usually include Ka-Bars. Knives over 4" or 5" often have to be kept off-base, in a locker secured by an SNCO, or in the armory.
- He probably won't/can't carry his gift knife in training or deployment, since he'll almost certainly have a gov't-issue OKC bayonet (very similar to Ka-Bar) to carry around. He can't just say "I don't want to carry my issue bayo", and that way he's not putting wear/damage on his personal knife if any really rough work needs to be done.
That said, I'm sure he's going to enjoy having his own personal Ka-Bar for the rest of his life, so no reason not to get him a good one now. Just understand that he'll have a lot of gov't-issue gear to use for the next few years.