Basically, I'm looking for a durable, high quality knife. It will be put through constant abuse. One day it will be immersed in salt water, animal entrails and fire, and the next it will be used to cut through rope and metal, break glass and occasionally pry open containers. Edge retention is a priority.
Quite frankly, that sounds like something I wouldn't do with any knife, unless I had absolutely no other choice and something important, like my life, depended on it.
If I were you, I would get a good fixed blade knife, and an entry tool like the Ranger Knives Entry Tool. The knife would cut well and handle skinning and rope, and everything else you could do with the Entry Tool, from hacking through car doors to chopping metal, breaking glass and prying open manhole covers or containers.
Now, if you really for some reason want to do all of this with just a knife, then I feel that few knives will be able to do the job. Knives with rubber or natural handles (most Fällknivens) are right out, because they will not like being near fire. Knives with stainless steel blades will not like cutting metal, they will chip their edges very quickly. Knives with carbon steel blades will not like being in salt water, their edges will corrode away with relative swiftness. No knife will like fire, because high heat may damage the heat treatment. It would be a compromise, but I would go with a Busse in the 5" + range, perhaps a CG Badger Attack TAC, or if you want something larger, you could go all the way to a CG Fusion Battle Mistress, although that would be an enormous knife, long and heavy, and very cumbersome in small tasks. There's a lot of stuff in between, too.
So, why Busse? Well, because of INFI. INFI is the steel used in Busses, and it is rather excellent. It is hellishly tough, which is good for what you want. It does not chip, which is good for what you want. It can take high temperatures better than most steels, which is good for what you want. It holds an edge very well, especially in hard use, which again, is good for your uses. And it's also very stain resistant, inspite of not being "stainless." A CG blade with a coating will only be able to develop rust in the exposed edge area, and if you wipe it clean after salt water immersion and preferably wash it with fresh water, you shouldn't have too much trouble with rust at all. Best of all is the warranty - you break the knife, Busse fixes it for you.
The downside to Busse is the relatively high price and also the relatively poor availability. You'll have to look for what you want in the secondary market, eBay and this forum's exchange forum and such, to get what you want, unless you get lucky in the Busse company store.
There are somewhat similar knives that could do well, like Ranger Knives, but most of them use more rust prone steels, like 5160, which might be an issue with salt water. However, they're much cheaper and much more available, so, it's a difficult choice.
But again, if I were you, I'd just get any good small to medium fixed blade, like a Fällkniven F1 or even A1 (for salt water use, you'll want it with the black coating), and on top of that, a Ranger Knives Entry Tool.
