Tough question! I think the WS Woodlore come close to perfect for this kind of work. The blade is plenty stout and there is no distal taper so the full thickness extends all the way to the tip. The tip itself is sharp enough to get pretty good penetration which is what you need to dig an arrow out. However, lateral prying MIGHT snap a mm or two off the very tip. I dunno. Personally, I would never pry with my Woodlore unless I had to.
I like sargey's suggestion of the Becker Necker. It's a pretty stout little blade.
In all my years of archery and stump shooting, I've never had to deal with this because my arrows have screw on points. I just unscrew the shaft and screw in a T handle specifically designed for this purpose. I think they even make them with a hammer slider so you can pound it out, much like the tools used to remove dents out of a car body. Are your field points glued on or screwed on?
Personally I would buy a small chisel, maybe grind on it a bit to thin it out, and carry a hammer head. A sharpened punch would work too. These are a lot cheaper than a knife and if you break one, just get another.
These are a little short for prying but something a little longer with some work on the edge might be just what you need.
Add a jarvenpaa puukko for cutting away the wood and you should be able to dig out the toughest field point or broadhead.
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