A Copper Clip is the nickname for an imperial copper coin in the Final Empire.
A clip is commonly used by Mistborn and Coinshots for jumping and attacking. Basically, they throw the coin on the ground and push upon it to fly into the air. Alternatively, they throw the coin at the enemy and push upon it to shoot it into the enemy's body, much like a bullet.
CLIP (COINAGE): The nickname for an imperial copper coin in the Final Empire. Commonly used by Mistborn and Coinshots for jumping and attacking." - The Well of Ascension