I haven't been here long, but I've noticed a lot of people don't bring much by way of a knife. I'm guessing this is one of the polarizing topics as I'm sure there are other people like myself who never go into the bush without a decent knife and others who insist otherwise. To each their own, lets just talk knives!
Folder vs Fixed
I'm partial to fixed blades myself for the bush. Most of my cutting is on wood and the thin handles of most folders are extremely uncomfortable to use. Folders are generally lighter and don't need a sheath, but I like the security and accessibility of a sheath.
Carbon vs Stainless
I've heard a lot of debate about this, but imo unless you're in a salt water environment it's more about preference. Stainless does have a lot more carbides and greater wear resistance. For bushcraft I don't notice a difference, I'm mostly cutting wood with the grain which causes next to no wear. I do keep my edges extremely acute to excel at that job, so most dulling is the result of deformation, a rolling of the edge. Hardness and grain size of the steel affect edge stability, how ever some stainless steels form very large carbides which can tear out of a thin edge, not an issue with modern particle steels though.
I've heard a lot of complaints that certain steels are hard to sharpen, in my experience this is due to people not knowing how to sharpen. You don't need special tools, even a 99cent sheet of wet dry sand paper will sharpen the fanciest steel. And if you take care of your tools you shouldn't have to be sharpening out large chips and dents. I can restore the edge on my S30V stainless knife from not sharp (by my standards) to hair whittling in a few minutes on a pocket stone and a few passes on a leather strop. It's all just technique.
Grinds & geometry
Theres a lot that could be said about this, I find that almost every knife I've bought had an unnecessarily obtuse grind, and over all a disappointing edge. Even $500 knives, and blades from custom makers. I think this is largely due to competing to offer the best warranty, as "bomb proof" knives seems to be the latest trend.
My preference is a slightly modified "scandinavian" grind (like moras), just one flat bevel on each side that goes right to the edge. My modification is putting a second "micro bevel" on one side to make the edge a little thicker and more durable and quicker to touch up (less steel to grind off of a narrow bevel) without sacrificing the acute angle on the other side which lets me lay the knife almost flat like a chisel, giving the best control and power when carving wood.
Otherwise I grind the edge nice and thin on a belt grinder, giving it a mirror polished convex edge.
Best out of the box edges I've found are the Fallkniven F1 with a thin convex edge and believe it or not, Mora's. Sometimes they're a bit dull, but still has the traditional scandi grind, so getting them up to speed is a breeze.
Sheaths: Style & material
For me, as a hiker, there's only one choice, dangler sheaths. They hang below your hip belt. I don't like wearing a knife around my neck, or attaching it to my pack.
Sheaths generally come in leather, kydex or codura. Kydex, a hardthermoplastic thats molded to the shape of your knife is definitely the lightest. All can be made as DIY, kydex is pretty easy to and very forgiving.
The knife that finally made me stop buying other knives? A puukko from the Finnish maker Jukka Hankala. Stacked birch bark handle, hand forged carbon steel blade, and a leather sheath so perfectly made that the knife "clicks" into it. 6 ounces with sheath.
For the city, a Buck Mayo TNT folding knife. CPM S30V blade, titanium handle. 2.78 onces.
