as a Marine, I would suggest....either a Good Ka-Bar, or a great watch tougher and more functions the better (i.e. suunto type, elevation, compass, etc.). He can take the gun with him he would just have to check it in with the Armorer until he gets married to a Jacksonville skank to get out the barracks.......LOL
All seriousness, Ka-Bar, 1911, or great rubberized digital watch.
A watch or multi-tool is good idea. My father bought me a Ka-Bar and a leatherman before leaving for Afghanistan. I still have both and they mean a lot to me. I never use the ka-bar anymore, but the leatherman goes with me anytime I'm camping, fishing, or hiking.