My view may be odd, but I think the blade shape matters LEAST of all the factors that make for a good fighter.
First thing, it's gotta be tough. Folders need GOOD locks. Blade steel needs to be at least decent. Strider fixed-blades have been so popular despite their ergos ("brick wrapped in string") because you just can't break 'em.
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Grip shape and general ergonomics is the next most important factor. That means a grip that retains well in the hand, and won't let your hand "slide down the blade" on a hard-target stab. The SOG that Combat-wombat was looking at has a nicely sculpted lower guard that prevents that sort of problem, and the ergos are otherwise above average.
A *really* good grip will let you put more power in, and quickly shift the tip around as needed, it'll "dance in the hand". Go play with a Mad Dog ATAK or bigger, or any Ernie Mayer big bowie, or a Bagwell (handmade if possible, or the Ontarios). Or a Larry Harley Battle Dagger. Or for the intended use, a big Himalayan Imports Khukuri. All of them feel "right", they feel like they merge with your hand.
Of all the "cheap knives" I've ever handled, believe it or not the Buck Nighthawk feels very good in the hand. Cheap steel, daily utility will have you cursing the sharpening process, but as a cheap fighter not half bad.
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Size depends on concealability requirements and legalities. Bigger is better. Period
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Is the edge any good? (read: will it cut? See also Joe's sharpening FAQ)
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Only once all THAT is sorted out do I even care much about the blade shape. I've seen tests against old ballistic vests. Barring a hard trauma plate I can assure y'all, they'll ALL blow right through, even a friggin' sheepsfoot if you hold it right and use some muscle. Arguing about the penetration ability of a classic Tanto versus Americanized Tanto versus dagger or whatever, it's just laughable, they'll all work. Even Cold Steel's weird "Nogales" point on the Vaquero/El Hombre/Desperado.
IF you can hang onto the sucker and it holds together.