I have before, but not your classic idea of a neck knife; I carried a Folder like that, and found it great.
For a couple years, I carried my Case Peanut around my neck in a custom kydex sheath I made for it. It was a lot faster than digging in a pocket for it, and a great bonus if sitting, I could get to it SO much easier then. I got out of doing that when I was doing a lot of machine and mechanics work; something hanging around your neck is suicidal then.
Lately with my light around my neck 24/7 (except time at the lathe in the shop) I have considered carrying the ‘nut that way again, but a lot of the convenience of the light hanging there is being able to turn it on and leave it hanging there to shine down… I tried it for a few days a couple months ago, and the knife hanging there either blocks it completely or adds a shadow in a bad/funny place. Might try it again for a few days and see how it works if I space them out vertically.
I had also tried a small fixed blade there at times, but the shear size of it(even in a minimal or skeletonized 5″ or less oal knife) was too big, it swings around a lot, and hangs down into my way when bending over working etc. The solution is to put it under my shirt or jacket, but then its a pain to get at to draw the knife, at that point I might as well belt or pocket carry it.
Its actually funny, one of my takes from the pass around box this week, is a small 6″ OAL dagger neck knife… I don’t wear fixed blade neck knives as said above… but I still kept this little knife… Its just such a nice size and setup for the knife style, it looked fun to have and try to wear. Will see now it goes I guess.
The peanut in its Kydex;
I have just now, while thinking this out, taken the sheath off of the para-cord, and put it on a short dog tag chain, and a S-biner. I can then hang it on the cord I use for my light in the same way that I hang the light.
Also shortened up the chain on the new knife to the same setup as the Peanut. Will see how it works around the house some time soon.
G.