Whenever I'm out and about, out of town, I always have a sheathed fixed blade on my belt. I've needed a knife quickly a few times in the past, and I know at my waist, its to hand in a hurry, using only ONE hand.
Lately, mostly, its been an M95 Peltonen. Light, great sheath, and sharp as hell. Great design, as is the shorter version.
Neck knives are a no for me, saw a guy nearly hang himself with one years ago, going steep downhill in thick brush. The advice up top is good, or wear it on something breakable.
In town, I always have a carbon opinel folder in a jacket pocket. light, unobtrusive, sharp, and I like the lock system.
When I was hunting bigger stuff, I usually had a Grohman skinner, in the pack. Quite a few of the hardcore guys here, guides and ex-guides, use Havalons.