KNOWLEDGE
It seems to me that most of the writers on survival emphasise knowledge above all: eg Mors Kochanski, "The more you know the less you carry."
When I first started reading up on the subject in a more disciplined and rigorous way back in the early 1960s after an appetite whetted by mixing with old soldiers as teachers or friends of my father, good books on the subject were few and far between. I well remember contacting the RAF Survival School and being thrilled to be sent the pamphlets they issued to aircrew.
Since our interest has become popularised by the likes of Ray Mears and Lofty Wiseman, good quality information has been much easier to come by: so too has poor quality information, but I suspect most experienced and knowlegeable members are able to tell the difference.
So KNOWLEDGE would be my answer to the question posed in the OP. Without knowledge, none of the items suggested would, on their own, contribute much to saving life unless there is knowledge of how to use them.
As someone has already said, knowledge has saved many people from getting into what ignorance would have been a survival situation.