Do you know Pen Tricks?

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I have seen a lot of people just whirling pen into their hands with so much professionalism which leaves one wide-eyed. Though I know only 1 Pen Trick, which is to Rotate the pen on my fingers, I love doing it when bored or when I come across something difficult to solve. I never use it as a show-off. Many people know amazing pen tricks, and I wonder, how many do you know? When do you use them?