If you can afford it, look at a Strider AR or GB.
If you can't... Emerson, Microtech and Spyderco are good. Spyderco perhaps being the best for the $.
But the Strider knives are on a level of their own... If I could only carry a manual folder (no fixed blade, no auto) then I'd save up for one of those bad boys. They are massive and have a lifetime warranty.