Let me add a helpful comment here.

In the old days I used to do the same thing as a lot of people ... compile a list of items that I thought would be helpful - or cool - to have in a survival kit. This approach could be termed the "itemized list" way of doing things. There is some value to this. Specifically, the itemized list method will help you to identify some critical items for your survival kit that you might otherwise have forgotten. For this reason alone, it's a valuable step to take.

Nowadays, however, I do not use the itemized list approach as my primary way of designing a survival kit. Instead I use a method that could be termed the "functional survival approach". It works along the following lines:

I identify the essential activities that will be needed to survive over the period of time that is required - for the environment where I will be located. These are simple things: travel (e.g. walking), food, water, shelter, medicine & first-aid, sleeping, clothing & staying warm/cool. Then I work through the steps that are required to effectively do each activity - and make sure I have sufficient essential equipment to accomplish the tasks. The functional approach takes more time - but is guaranteed to be more reliable because you are forced to ask yourself exactly HOW you are going to do things.