Well, I'm in the army, not the Marines, but the rules regarding knives are fairly similar from what I understand. First off, something really nice like a Reeve or Randall or any other good sized fixed blade will likely cause problems. I brought a Ka-Bar here to Korea with me based on erroneous advice and had it confiscated at customs. It won't be confiscated in the States, but it would have to be stored in the arms room. A very useful gift would be a multi-tool. They're ubiquitous within the service and you end up having a million and one uses for them. I carry a Swiss Tool and a Camillus EDC on a daily basis. Simplicity is the most important thing; fancy stuff will only break or be a hassle out in the field. I'm very happy with the performance of my EDC, so I would definitely reccomend one of those. However, I have a lot of experience sharpening and the recurve on the EDC would be difficult for a novice sharpener, unless he has a Sharpmaker. So I would base that decision on your son's skill and tools for sharpening, since a dull knife is basically useless. The M-16 Military series from CRKT looks really nice; I have one of the original aluminum handled M-16's and it's great. I don't know how your son feels about partial serrations though. They certainly have their uses, but it's all about personal preference. I'm having a hard time thinking of any others right now, but these are two I have personal experience with. I'll think a little more and post again later, I have to go back to work now. It would also help to know what your budget is. Oh, and whatever you get, DO NOT let him take it to boot camp!!! He won't keep it past the first hour, not without facing serious consequences. I would actually suggest giving it as a surprise gift at his graduation ceremony. At that point chances are good he could actually keep it with him. Best of luck to your son in the Marines.