Sometimes it’s the small things that drive you crazy for ages, without your really noticing.
One of these is that many pens have a cap which can be placed on the pen’s barrel-end so that the clip presses into your hand.
Today’s invention is a pen with a key (blue) moulded into its surface corresponding to a slot in the pen’s cap (red).
This ensures that the clip will always be attached in the correct orientation -ie without colliding with one’s hand.
A better design would involve a cam-shaped slot, so that just pushing the pen top on would cause it to rotate into the right position.