I've probably used emergency fishing line for repairing stuff more than I ever have fishing. Good cordage is an absolute must in any kit in my opinion. Of course you can always strip 550 cord down for smaller threads but fishing line is neat stuff.
Survival, in my opinion, is not about having specific gear for specific tasks. It's more about being able to improvise items to do things that they normally wouldn't do. Thinking outside the box.
A funny thing is I have given away survival tools and gadgets in remote villages in South America and it never fails that the indigs will always amaze me by using some component for something I never dreamed of. I guess it's a mentality of not having the traditional mindset of doing something one way or even knowing what it's suppose to do that allows their imagination to take over and make something useful out of something not designed to do that task.
I think the technology and comfort we enjoy has killed a lot of our survival skills.