I agree the Axis lock is excellent for one-handed opening and closing.
Other excellent lock styles, IMHO, without commenting on the overall quality of the knives that usually use those lock styles:
* SOG's Arc lock.
* Cold Steel's Triad lock.
* Several of the Spyderco locks:
- The compression lock on the Para millie 2, as someone noted.
- The back lock on the Native 5, and the Chinook 3, is very easy for me to open/close one-handed, after you get used to the mechanism and wrist action required.
The cool thing is, as knife owners today, we have more choices than ever of excellent technology (in steels, in handle materials, in sharpening tools, in sheaths, and in locking mechanisms) than we've ever had. What's the coolest thing, to me, is how the "best" technology tends to trickle down and become available at lower price points. For instance, a new high-end custom folding knife implements a clever idea for a really strong lock. Then before long, some production knives implement a similar approach. And eventually, you see versions of that same locking system showing up on $30 to $50 knives. And of course, a $40 knife's lock is not going to be QUITE as good/strong as the lock on a $1200 custom knife it was based on, but it's probably a big improvement over the type of lock that was previously used on lower-end knives. A good example is the Cold Steel Triad locks. My understanding is these locks borrowed aspects of the Benchmade Axis lock system, and now you have Cold Steel folders such as the Voyager using this excellent lock system, for as little as $30 to $40. That's an amazingly good lock for a fairly inexpensive knife.