My guess is that we are all tool collectors.
While doing any particular job, I find that if a particular tool will make the job easier, I'll buy it (if cost is within reason) and figure that I got the tool for free with the money I saved by doing the job myself, rather than by paying someone to do it for me.
KNOTS:
We all know the story of how the rabbit comes out of the hole, goes around the tree and back into the hole, in making a bowline.
Here is a video of how I usually make it a little quicker, where with a twist of the wrist, the rabbit is already out of the hole.
This gent shows how to do it around one's body, but that isn't necessary.
Another knot that I often use is the "trucker's hitch"
There are a number of ways to make it. One more elaborate than another, but if you know how to make a slippery half hitch, this method is easy, and the method that I usually use.