I'd say that one of the rescue/assist knives must obviously be considered for a first aid kit. Even better, within reach of the driver's seat in the car.
Assist with glass breaker fits the bill. (reminds me, I want one, too )
For a Multitool I recommend the Victorinox Swisstool. I have the old one and like it a lot, but the new one is fine, too. Would I put it in a 1st aid kit?
Depends where you are going. For most situations it would probably be overkill as we're never far from professional rescue but alone in the wilderness the situation changes...
There are no fixed blades that come to mind for a 1st aid kit. I'd always take a folder to make the kit small and light.
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