All the ones mentioned are great, but most of them are kind of big, IMHO.
I've tried a number of them & these are the best ones, for me:
HAK (HideAwayKnife): I have the plain utility model in 440C. Get it sized right & it won't go anywhere, not to mention, no one's going to disarm you w/o getting their share of wounds.
Spyderco SPOT: These are getting harder & more expensive to find. With the finger hole & handle, even the biggest hands (Mine are XXL) can use this.
There's an AUS 6 model (Which I've never used), & the nicer micarta scaled one, with VG-10 (I've had 2 different ones). The SPOT's sheath is probably the best of the bunch, because the "tube" that runs along the top, does keep the sheathed knife from flopping/turning.
Emerson La Griffe: These are probably the least expensive & easiest to get. Their blade is larger than the SPOT, but smaller than the HAK's.
I have had a MicroTech Manus, Benchmade 210 & Tether, Buck/Hartsook, Ranger Little Bird, Tops Wolf-Pup, Blind Horse Bat-Wing, CRKT Dogfish & SideHawg 2, Livesay Thrasher, & probably a couple more I've forgotten.
I'll admit I'm prejudiced towards neck knives with a hole in it. I like that because it's easier to index, pull-out, & retain, in the time of need (& yes, I've used mine).
I've never handled one, but I would say the best "inexpensive" knife I've seen that I wouldn't mind trying out, is CRKT's A.G. Russell Ringers. Particularly the Hawk-Bill one, as it has an OAL of 3 1/2" (Like my large HAK, 5.0 2-finger ring size).
Out of all those knives, I still have the 3 main ones I listed above & a custom Little Bird. I did like the Livesay Thrasher, but preferred the B/M 210 over it, due to its better steel (S30V vs A2, as SS is nice for a neck knife).
Good luck with whatever you choose.
