There are a lot of tools that are important but I saw one response that said release aid. Since most of us bowhunters use one, we would definately have our day end early without it. That being said, my most important tool is my backup release in my pack. I have dropped my release at least 6 times that I can recall after climbing up a tree and getting all my stuff setup. It's a real pain to climb down and get it, not to mention that I usually work up a sweat doing that.