These are the neck knives that I carry fairly often.
Left to right: Hogue EX-F03 Purple, Spartan_Blades Enyo Bronze Line Field Grade (AUS-8), CRKT Folts Minimalist Bowie Neck Green, MKM Jesper Voxnaes Mikro 1, Bradford G-Necker, Kizlyar Supreme Amigo Z Orange, Spartan_Blades Enyo Elite Gold Grade (S35VN, sheath by Eight2Ten).
The one I carry most often is the Spartan_Blades Enyo Bronze Line Field Grade (AUS-8), which has an excellent sheath. The sheath that came with the Enyo Elite Gold Grade was unusable, even after leaving it in a hot car in Florida sun for a couple hours; the sheath shown here is by Eight2Ten and draws the most compliments from chicks, but I'm too old and too attached for that to do me any good. Both Enyos were very dull out of the box.
I like the orange Kizlyar Supreme Amigo when I wear a blue shirt because Go Gators and I like the ring. The blade has been fine since I sharpened it near the heel.
I love the Hogue handle, which was a nice surprise because the two Hogue folders I have need chamfering on the handles. The blade is rather small compared to the handle, and I am not fond of 154CM, but on the whole it's a good knife.
The next-to-worst neck knife I have ever handled was a Benchmade Follow-Up. It had jimping all over the handle that made just about the entire handle a hotspot. The sheath was OK.
The worst neck knife I have ever handled was a Bark River Harpoon Necker. It had a full tang that protruded way above the scales and had rather sharp edges. The magnetic sheath had zero retention. I sent Bark River an email asking if the sheath would be covered under warranty; the reply said that it was covered, but that was long after I had sold the knife.