My vote if you can get one is Strider knives AR.
I have used a plethora of "Hard Use" folding knives including a Chinook 1 (not the new mod). Frame locks from Reeve and Mission. They all have fallen short in one way or another. No failed locks out of any of them, they just didn't do it. The 440V Chinook would not stay sharp very long and had a very thick edge. The Mission Ti blade would dull just sharpening a pencil and the Reeve Sebenza has blade too thin for hard use. Never broke one, but it did not inspire confidence like the AR does. The Al Mar Sere 2000 had a lock that would slip, even after scuffing the tang and lock face. The list goes on.
I cut and pried through a steel filing cabinet at work with the Strider, pried open doors and windows. It will even cut my apple at lunch, and sharpens pencils with out dulling.
In other words it does the nasty stuff and still can do the light mundane work as well.
It is big, but not too big. It stays sharp and is strong as hell. It is the ultimate in strength and cutting ability. And last but not least, its a great impact/control tool when deployed in it's closed position