SXA allows you to create sites and tenants really quickly. If you ever created a site with wrong features or simply created it to learn new functionalities, you probably tried to remove it. Doing it manually is time-consuming as sites and tenants contain items in locations other than content as well.
Once you start working with SXA you might be overwhelmed by the number of available renderings. The toolbox is a great feature which lets you drag and drop renderings on the page though sometimes it might be hard to find what you are looking for.
I present you Unicorn Dependency Graph Generator. It will give you a bit more information about your unicorn configurations and solve problems with missing dependencies.