The best box cutter is the Moby Safety Knife. I used it when I was working in a supermarket 20 years ago, and I haven't found anything even remotely comparable.
The short blade on top is perfect for breaking the tape to open the box without damaging the contents. Then the mouth can be used for quickly breaking down boxes or cutting shrink wrap. You are just cutting tape, so the blade never wears out.
I cringe every time I see someone using a Stanley knife in a supermarket.
I learned about the Pacific Handy Cutter from my local grocer. It's cheap and excellent. It has a dull edge for 95% of tape cutting needs, and a safety guide for when you need to use the blade. Admittedly, it's not useful for slicing up / cutting down boxes.
This model is right handed, but they make a lefty too.
I remember someone talking about their $100 box cutter and thinking, huh? I just use my keys.