I have 3 hideaway knives by Mick Strider. I like wearing a one-off prototype as neck knife. Like above posters, this is a 'last ditch' weapon, not a utility knife. Because of this, I don't use the blade.
Have a bunch of others like CS, Newt livesay, TOPPS, etc. but they're all a bit too big for regular carry.
I would suggest a folder for common utility, it's easier to access as well as doesn't give away the presence of your 'necker.