I agree with what Ace Rubber Chicken said. I keep a titanium (I like it for durability and anti-corrosive properties) knife on the inside of my calf out of the way, and a small titanium knife on my bc strap. The calf kife is blunt tip for prying, etc because it's bigger and gives me more leverage, and the bc knife is pointed. Some feel it should be the other way around; blunt on the bc so you don't poke yourself, but I have it in such a way that I need to be completely narced to do it (hasn't happened yet, and god willing, it will never happen).

Also to consider are your intended uses. Other can speak to this better than I can, I'm sure, but material choice is big too. Different stainless numbers have durability, sharpness edge holding properties, weight, corrosive resistance, etc. To me, sharpness is not so important. I keep mine super sharp as I have access to professional sharpening in my kitchen (remember, I'm the fooddude). Also, as long as a knife is reasonably sharp, it will cut you free of most line and monofilament I come in contact with.

I now carry shears as well in case I have limited "sawing" movement in tight places, I can just snip! I take a case of EMT/Surgical shears from the hospital and use them as disposables throughout the diving year. I bring many extras on boats for others in case someone is missing one or it's rusted and not functioning properly. We all need to look out for others, especially since we may need their hep down below.

Good luck, and remember... it's a kinfe. Not a major investment. If you but it and don't like it, it becomes a spare!