My grandfather gave me a Buck 110 from the 1970's era. Brass body, heavy, impractical to carry without a pouch sheath. It is among my most prized possessions, for sentimental reasons.
In these more modern years, the more important knives to me, those that won't be sold or traded, are those where I interacted with the maker to customize a knife to my specifications. I have yet to sell a truly customized collaboration knife. Most of those were with David Broadwell, John W Smith, and Larry Chew. David, especially, is an amazingly versatile talent (not that John and Larry aren't). David's breadth of skill is stunning. Check out his web site. Pens to knives ... subhilts to modern folders. Tactical to art. Knives and swords. Amazing talent.