Airborne, welcome to THR.
I tried several different knives while deployed to OEF in 06-07. Some actually were used during combat, though they were used as "combat" knives are generally used, to get things done rapidly in tough conditions, not to directly kill anyone. We used support weapons for that.
One knife I used was a
very sturdy knife made by good friend Shane Justice. It has a 5.5" blade with about 4.75" cutting surface, not huge, but good for lots of jobs. Even that was hard to pack around in a quickly accessible manner with all the stuff you have strapped to your IBA.
An even better solution was an On Scene Tactical Speed Dialer sheath and Waved Spyderco Endura. This gives you a very size-efficient knife that has a 4" blade, so it can be kept in the barracks even in the U.S. It deploys as quickly as a fixed blade, but takes up much less room, and is lightweight. It can also be clipped to your pocket when you're not in IBA.
If you want pictures, try to find a December issue of
SWAT magazine. I wrote a short article about it.
Be sure you have a good multi-tool, and a red lens light. For general utility use, a MiniMag Lite with red Night Ize LED (available at Wal Mart) works great, is brighter than the incandescent bulb, and batteries will last several times as long (about
30 hrs!).
Take care, and keep your head down.
John