If I was going back to Iraq or Afganistan I would definitly get a SOG multi tool.The issued Gerbers are ok but don't last as long as the SOG's. I went through 3-5 Gerbers or Leathermans in Iraq between braking them (Gerbers) or people stealing them (Leatherman's). For 50 to 75 bucks you could get him a SOG multi tool and get a good folder from Benchmade, Spyderco, or CRKT.
I wouldn't get him any type of auto as some commands are funny about soldiers carrying them (even though everyone already carries a firearm with ammo on them
Customs also confiscates them when the units come back ( if he doesn't take care to keep it out of there sight, personal experience). For what you spend on an auto you could buy 2 or 3 good regular folders. I still have both of the folders I used over there and they still work great
If you decide on a fixed blade I would keep it down to around 3 inch blade, you would probably want something that is short, light and very sturdy, no huge Rambo knives that are going to get in the way more than help do the intended job.
Just my .02 cents of experience. Hope this helps and good luck to your cousin.