Fluorine is used in the production of low friction plastics such as Teflon, and in halons such as Freon. Hydrofluoric acid (chemical formula HF) is used to etch glass in light bulbs, and for similar applications. Monoatomic fluorine is used for plasma ashing in semiconductor manufacturing.
The first commercial production of fluorine was for the atomic bomb project in World War II, where the compound uranium hexafluoride (UF6) is used to separate isotopes of uranium. This process is still is use today.
Very small quantities of fluorides in drinking water are believed to prevent dental cavities, although it can also cause mottling of teeth in children.