The story that WD40 (Water Displacement 40) is basically fish oil is a myth.

It is actually:

Solvent naptha petroleum, medium aliphatic 60%

petroleum base oil as paraffinic distillate, heavy, silvent dewaxed (severe) 15% to 25%

corrosion inhibitor unregulated 1% to 10%

wetting agent unregulated 1% to 10%

fragrence unregulated 0% to 1%

carbon diaxide 2% to 3%

WD-40 was created in 1953 by three technicians at the San  Diego Rocket Chemical Company as a a rust preventative solvent and degreaser to protect missile  parts..

They were successful  with the fortieth formulation, thus WD-40.  The Convair Company bought it in bulk to protect their atlas missile parts. Ken  East (one of the original founders) says there is nothing in WD-40 that  would hurt you.

For a long list of what WD can be used for, the makers ahve agreed:

Protects silver from tarnishing.  

Removes road tar and grime from cars.  

Loosens stubborn zippers.  

Untangles jewelry chains.  

Keeps ceramic/terra cotta garden pots from  oxidizing.  

Keeps scissors working smoothly.. 

Lubricates noisy door hinges on vehicles and doors in  homes.  

Lubricates gearshift and mower deck lever on ride-on mowers

Rids kids rocking chairs and swings of squeaky noises 

Lubricates tracks in sticking home windows and makes them easier to  open..  

Spraying an umbrella stem makes it easier to open and  close.  

Lubricartes and stops squeaks in electric fans.

Lubricates wheel sprockets on bicycles, tricycles and wagons.

Keeps rust from forming on saws and saw blades, and other tools.   

Keeps bathroom mirrors from fogging.  

Lubricates prosthetic limbs.  

Keeps pigeons off a balcony rail or window ledge (they hate the  smell).  

Removes all traces of duct tape.

Cleans and removes bugs from car grilles, bumpers and paintwork.

Displaces moisture from the distributor head of an old car engine.