Blade size, shape and materials: 5.5-7in. long, clip or spear point, .20+ thick. 440c,vg10 sv30,5160,1095 (I could care less, if its heat treated right the perfomance will be too close to call). A slight drop or cant between the blade and the handle.
Handle construction, size, shape and materials: Full tang or as near as possible. At least 5in. long. Micarta, Krayton/"wunder gummi", or Strider wrapped cord.
Sheath construction and materials: Leather or nylon with a protective insert. It should give enough drop to put the butt at or below my belt-line to clear my other gear. An added plus would allow it to be carried high ride as well. The older strider sheaths were great.
I've used quite a few knives over the last few years but they all seem to share some of the things above. My favorite of all time is my Simonch Raven Combat. I have never used a better knife. Others that fit in are Fallkniven A1, Peltonen Sissi knife, Strider MT-L, Dawson Victory, Chris Reeve Projects 1&2, Nkonka (make it 6in with a beefier tip an I'm all over it), Busse NO, SFNO and my newest addition an M6 from Swamp Rat