1. CRK Small Sebenza - Drop Point - S30V - I've had this one for about 12 years. It went on every Scout trip I went on with my kids. Apart from the history I have with it, I find it to be virtually perfect in all respects. When I got the knife below, I made this one my dedicated backpacking/peak bagging knife.
2. CRK Small Sebenza Insingo - S35VN - IMHO, the perfect edc knife. I carry it virtually every day.
3. KBar MC - Mine's 33 years old now. Carried it for 10 years anytime I was in the field as an infantryman. Not the world's best hard duty knife, but it served me well enough/never let me down. I don't use it anymore, but iy will always be in my collection.
4. Victorinox SAK - I carried this one on duty as well. Actually used it a lot more than the Kbar.
I could live just fine with the above four, which are my real must haves. If I ever lost any of them, the only one's I'd replace are the CRKs.
If we include multitools, I'd add a LM Wave and PS4. I always have one of these on me (usually the Wave). I use them almost daily for some on the spot repair.
If we opened this up to include the knife I'd really hate to lose, I'd add my CRK Mnandi (Thuya Burl Wood) It took me a very long time to find one that spoke to me the way this one did. I let a really nice one go about four years ago (Honduran Rosewood) and regretted it until I recently pulled the trigger on the Thuya Burl.