The best folder lock I know of in terms of reliability and strength is the Barry Wood "swing lock". It has its drawbacks, they are not practical to open one-handed, and the design dictates a mostly straight and not outstandingly ergonomic handle shape. But they work pretty well for general utility, and are essentially a fixed blade once you get them open. You can't really break them.
After that, I like integral locks like the Apogee, Sebenza, MPF, and Pinnacle. They are plenty strong, brute simple, and when you grip the handle, you pretty much hold the lock in place.
Next, I like the REKAT Rolling Lock. It is plenty strong, hasn't demonstrated any tendency to fail in any way, and the side release is very easy to use and out of the way.
In a virtual tie with the Rolling Lock is the Benchmade Axis lock. Again, plenty strong, reliable, simple. I give a slight edge to the Rolling Lock because I personally like the side release better. The Axis has the advantage of being ambidextrous though, and also has redundant springs.
Then there are a lot of button style locks on knives like the SpeedTech Synergy, TiKnives, and numerous autos.
Liner locks can be good too, though they are at the very bottom of my list. You have to evaluate them on a knife by knife basis. It would take a really exceptional knife for me to ever buy another one. I saw some gorgeous Phil Boguszewski folders at a recent show that almost made me write a bad check.
I tend to prefer mid-locks to liner locks for small utility pocket knives. I like that I can unlock my Boye folders and BF Native with my hand in the natural grip. Seems easy to me, but that's a personal preference thing.
I like butterfly knives a lot too. They can be very strong and reliable, and have ten times the fun quotient of any other folder.
