My favorite knot, easy to remember and used every day, is the shoe tying knot that won’t come undone on its own but is as easily untied as the regular shoe knot. The only difference and the secret is to go around the initial loop twice instead of once and continue as normal. It won’t come untied and can easily be undone by pulling on the ends. The only downside is you have to start with the proper side a little longer or the finished knot will be a little “lopsided”. Try it on that pair of shoes that keep coming untied.