Active duty Marine here. A multi tool or good folder will see the most use just doing the basic tasks. But that isn't what you are going for. I have been carrying a Winkler Belt Crusher with the sculpted micarta handles on my off hand side for a while now and love it. One thing to consider is the environment he most likely will be deployed in and how that will relate to his gear. Such as a stainless vs carbon steel vs a carbon steel that is coated, the amount of grip afforded in adverse conditions, the overall purpose depending on fighting knife or more utility, etc. The sculpted micarta scales give me grip no matter what the conditions and the leather kydex hybrid sheaths they have mean that the knife goes in and out silently. Another factor to consider is the attachment methods. Some sheaths are not able to attach to your plate carrier because of how they are designed. Also I would consider the ride height of the sheath. If he is like me and chooses to carry it all the time, then you want something that will keep the bottom of your sheath still hidden beneath your cammies. I find that the Winklers fit me very well and have some of the best factory edges I've ever seen. They also fit the parameters of what I need. The Belt Crusher specifically has a rounded glass breaker which is a plus. I may cycle through my folders that I carry, but I don't go out in my cammies unless I have that Winkler on my hip. I hope this helps a bit! Let me know if you have any questions or want some insight.
