Rosin

Rosin is the sap from pine tree. It is a sticky substance but can be processed and used for:

Rosin is commonly used as a flux in metallurgy, especially for soldering.
Bowss for musical instruments such as the violin are normally rubbed with rosin to increase the grip on the strings.
It can also be used to demonstrate resonance in aluminium bars by stroking them with rosin tipped fingers.
Ballet slippers are rubbed in powdered rosin to reduce slipping.
Baseball pitchers use a rosin bag to keep their hands dry. Usage of rosin is specifically mentioned in major league baseball rules[1]