Alert: You'll still get emails from people who accidentally deleted their account, but at least you tried.
Badge: Eventually this custom CMS you're probably building is going to need tags.
Checkbox: People need to be able to accept the terms and conditions they don't read somehow.
Description list: For when you need to take the data from just one table row and somehow turn it into its own entire table to keep the page from feeling too empty.
Dropdown: Probably the number one reason you're looking for a UI kit in the first place.