So, What is useful?

I am going to start out asking for help. Please tell me what is truly useful to you. Whether it is your do-all pen that makes you feel good or that dohickey whatchamacallit in the kitchen or shop, what adds value to your life. Or is it a book or quote that helps you? Please, do tell! I know that this is short after such a long time, but there will be more soon, promise (and your replies are of value to me and will give me the energy to keep blogging, so please write, even if a short comment, Thanks!).