Having retired after 22 years, mobilized, etc. I would suggest the following: A three layer Swiss Army knife with scissors, a multitool chosen for the pliers, not the accessories, and a good folding knife - no fixed blades.
The Swiss Army knife scissors are great for personal grooming, and the other tools generally shaped better than most others, are durable, keep clean, and won't rust. The main blade sharpens easily, the pen blade very sharp, the little-used can opener sanitary and easy to operate (not many sealed cans in military chow these days.) The tweezers and toothpick are nearly indispensable. For a personal knife, it's actually the #1 choice.
The multitool is either a long nose or modified pliers. Each has it's exclusive strength. The long nose does well, but usually can't grip well, and eventually gets twisted. The modified short nose grips much better, but won't work with smaller objects or in tight places. The latter is much less likely around military equipment, and tightening fasteners to the proper torque with pliers problematic. It becomes a personal judgement call. Multitools with gear operated jaws seem to be a good answer until one realizes the handles spread much further on large nuts and become a two handed job. I would recommend Leatherman or Victorinox for a multitool.
The folding knife should be a flat ground drop point with G10 grips. Those specific features work well as a utility cutter and are very durable. The blade does not have to be black, matte is acceptable as the knife will be carried in a vest pocket contained with a flap. Most black blades will lose their finish rapidly in the typically abrasive field condidtions. Choice of lock is up to your perception of which is best - but many have done well without a lock at all. Few issue knives had any for decades. Avoid knives with any advertising on the blades, or prices above $100, because they get lost, broken, loaned, or stolen. I think many here would recommend the Spyderco Tenacious, Benchmade Vex, Buck Strider series (avoid the 420 steel models,) and many others similar.
Fixed blades wind up in the bottom of the duffel bag 95% of time. There is so little space on field gear, and so much weight as part of the 65 pound average combat load many leave them behind. Some team members do use them - and they do make great trade goods - but they are often primarily a sharp prybar, not the role for an expensive custom knife made from high alloy steel. Any 6" carbon steel blade with a plain handle in a hard sheath will do. Retention and a tight fit with no noise are almost more important than the shape, size, or type of blade grind. The sheath needs to be MOLLE compatible, and the overall appearance of the knife without any decoration or high speed low drag tactical styling. Low tech low speed is actually the professional standard in the regular Army because it's unpretentious and realistically frugal. Smart soldiers save their pay for more important morale devices like Ipod tune players or laptops. Good fixed blade makers include Kabar, Ranger, RAT, and those who specialize in simple hunting knives.
That's been the real choices long term among soldier who use knives in the field - as opposed to those who carry them, which few actually do. There aren't many uses for knives these days in the prepackaged and tear open logistics chain these day. Even ammo comes in twist tied crates and easy open wrap the last 30 years, although most civilians have no clue it's that way. The days of prying open crates and opening drums with a big battle blade never really existed, anyway.