Very definitely a leather sheath. There's a lot of variations in the multiple mounting world. I use horizontal straps and removable belt hangers and danglers- some people use screw mounts for various vertical and horizontal carry options- talfuchre, I believe, has done a fair amount with "I" or "H" frame mounts.
I prefer horizontal wraparound straps for reversibility (I'm a leftie) and ability to slide random things I carry into them- like a widgy bar.
Frothe knife- there's different ways to do the handle. You can go fairly short on the 4 1/4 to 4 3/8 side and have a rounded butt so you can palm heel the blade, or go a bit longer in the 4 1/2 to 4 3/4 range for a more secure hammer grip. In any case, I don't like the spine side sticking out all poky past the end of the centerline of the butt. Doesn't make for any comfort when using anything other than a hammer grip.
Broad, relatively thin blades. I'm a big proponent of the 3/32 and 1/8 thick broad blades - they track well, you can choke up in a pinch grip, and they work better for food prep. 90% of what you do is food prep. Say it again- in the end- 90% of what you do is food prep.
Any decently heat treated steel will work- I prefer 15N20 and 10xax steels as you can get the absolute most in terms of a differential temper and fine tuning out of the basic steels, even though some other steels are much harder. I prefer 5160 in thicker blades, a twisted version of a differential quench (diff tempering 5160 is rough as it tends to tweak on air hardening and not do what you wanted it to)
Any handle material that's stable is good to go. I really like micartas as much as I tried to hate them. But some native north american woods are really excellent- bocote, ironwood, osage, and especially walnut. People tend to forget about walnut, but it's really dead solid and reliable stuff once you dry it well and give it a good oil and wax finish. Think gunstocks.
Edge geometry is really really crucial. I won't say any more on the subject than that- because different steels and heat treats and styles work better or best with different geometries- but the one thing that's at least as (and possibly even more) crucial as/than heat treat for the blade itself is edge geometry. Really important.