Are never just used for sweeping the porch. Almost all of them in the magical world are powerful flying machines and in the hands of a skilled flyer can get up incredible speeds. The golden rule here is not to get in the way of the broomstick or its owner/flyer. That can't end well - for you.
Not a painful medical affliction as some have suggested but a powerful magical aid which enables its owner to see a short way in to the future and to see what their enemies are up to. Owners of crystal balls really will know what you're up to and are not to be crossed (or you will pay a very heavy price indeed).
Mainly kept by witches as familiars, these cats are usually ill tempered (other than with their owners, cats really are not stupid) and are not playful little kitties by anyone's stretched imagination standards. They (and their owners), if you are lucky, will only scratch you. You don't need to know what happens if you're unlucky (though it would pay to cancel any immediate or pressing engagements).