I haven't served (except for that secret trip to Cambodia

) but I have read many of these threads and I do have a good sense for what works and what doesn't in the field.
First of all, with all due respect to the venerable Buck 110...don't. It may have served some well in 'Nam, but c'mon guys - that was over 30 years ago, and you can do better now. The Buck is bulletproof, but simply waaay to heavy and bulky to carry around. It also does not open one-handed, and that is not just a luxury in the field, it is a must, especially when you have to look hard to find a knife these days that's not a one-hander. There's just no good reason to not go one-handed.
For an affordable knife with the basic size of the 110, much lighter, with one-hand open and a great pocket clip, I humbly submit....the SOG AutoClip. The clip acts to fill the hand, and it's unique thumbwheel tension make sit super-secure if you're worried about losing it.
For the military, you're going to want a good multi-tool, a good fixed blade for heavy applications and some prying, and a folder for cutting small stuff that doesn't warrant a combat knife. I would take a folder that could also be carried in the pocket when on leave, for protection off-duty, etc. (If you're planning on using a folder as a weapon while in the field, you're in the wrong army!)
Tool - Victorinox SwissTool (unless you need needlenose pliers, then I'd go with the Leatherman SuperTool or Wave.
Fixed - standard KaBar or CS SRK ("second" is fine)
Folder - SOG AutoClip or mini, BM Griptilian, KaBar Dozier, Spyderco Native or Native III.
All these together can be had for less than $200.