When I first joined the infantry, I carried a foot long antitank KA-BAR. After about 5 minutes, I realized this was a mistake.
Now, 5 years later, I swear by my Gerber and my 'cricket'. The Gerber was issued, and the CKRT was picked up for cheap. This is the one I have.
http://www.crkt.com/Crawford-NECK-Black-with-Olive-Drab-Cord-Wrap
The wrapping is excessive, but makes it easy to hold through a gloved hand /in the rain. The blade is very thick, so you have no fear of breaking it. The tanto tip is very useful, and I have used it for everything- cutting 550 to digging holes.
IMO, all you need is a short blade. Unless, of course, you are Scuba Recce Ninja Master Sniper qualified.
The Gerber (or any multi-tool) is essential in my experience. I can not count the number of times I have heard "Hey does anyone have a Gerber I can use for a 'sec?" I keep mine on a carabiner, hanging from my TV, and it gets used, frequently.
As other members have said, expect to loose anything you may have. Whether it falls out, gets ripped off, gets stolen, gets broken, or some random guy "borrows it", thing just have a tendency to go missing.