Well a “good” knife for someone might be something inexpensive with solid performance. That $13 Smith & Wesson might work perfect, or the $30 CRKT. Some might not care about price and have no problem dropping $350-$1000 on a premium custom Osbourne, Kramer, Reeve, or Onion knife. Consider the use-case though too: is is a working knife that will get a lot of abuse and use? Or is it a pocket queen that might open an envelope or cut a wrapper every once in a while? Do you need corrosion resistance (like if you live near the beach or hot, humid climate)? Do you cut a lot of tough medium (boxes, paper, carpet).
Personally I’ve used a lot of knives and sharpened a lot of knives too. Leatherman, Kai Group aka. Kershaw makes a nice knife, CRKT does too for cheap. Victorinox also makes nice ones, and I’ve had great luck with Cold Steel products and KA-Bar. I own a Protech auto knife I bought in 2001 and it’s fantastic. Never missed a beat, snaps open and locks super tight. 154CM blade holds an edge forever and takes a very fine edge. However, it’s expensive and I don’t use it much anymore so it sits in a drawer.
Know what knife I use the most? A $20 Chinese otf knife with a no-name blade steel and chunky die-cast aluminum handles. It just works…cuts stuff, and is easy to sharpen. I also use a very well-worn no-name 3-blade knife I found once with Bakelite handle scales and (probably high carbon steel) nicely patianed blades. Takes a very fine edge. I also keep a Schrade 3-blade in the car. Cost about $18. I’m fine if they get lost or broken since they’re cheap and easy to replace. Even if I could drop big bucks on a high end knife, I still wouldn’t carry it around…only takes a second to misplace it, fall out of your pocket, or have your car run stolen with it inside!