My knives get used, but stay razor sharp. My two most used knives are the Rat Cutlery Izula and the Chris Reeve Sebenza. I have others though. I usually carry a knife, but not every day. I really like carrying a small fixed blade now, but I really love my Sebenza, so it's a mix. I have a little training in edged weapons, but it's not something I see using. i carry a Surefire LX2, E2B or E2D LED usually, along with Sabre RED on my keys. The one thing I was interested in learning was handgun retention with an edged weapon. Very interesting, but again, not something I really see using. Although, it's nice to know the little that I do.
If my main reason for carrying a knife was defense, I'd carry the Emerson or a Hinderer. I really like how quick the Emerson is to open.