Answer:
There are several different kinds, but the one you pick doesn't do its job. What is it?
What is it that no man ever yet did see, which never was, but always is to be?
What an fill a room but takes up no space?
i'm popular for Knuzlocks what am i
How can you burn an apple, blueberry, rose and pumpkin without leaving any ashes but retaining the smell of it?
You use it between your head and your toes, the more it works the thinner it grows.
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?