Used by most people on the planet at one time or another I found the history about it was rather cool.

>Water Displacement #40. The product began from a search for a rust
>preventative solvent and degreaser to protect missile parts. WD-40 was
>created in 1953 by three technicians at the San Diego Rocket Chemical
>Company. Its name comes from the project that was to find a "water
>displacement" compound. They were successful with the fortieth formulation,
>thus WD-40. The Corvair 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. When you read the "shower door" part, try it. It's the
>first thing that has ever cleaned that spotty shower door. If yours is
>plastic, it works just as well as glass. It's a miracle! Then try it on
>your stovetop... Voila! It's now shinier than it's ever been. You'll be
>amazed.
>
>Here are some of the uses:
>
>1) Protects silver from tarnishing.
>2) Removes road tar and grime from cars.
>3) Cleans and lubricates guitar strings.
>4) Gives floors that 'just-waxed' sheen without making it slippery.
>5) Keeps flies off cows.
>6) Restores and cleans chalkboards.
>7) Removes lipstick stains.
>8) Loosens stubborn zippers.
>9) Untangles jewelry chains.
>10) Removes stains from stainless steel sinks.
>11) Removes dirt and grime from the barbecue grill.
>12) Keeps ceramic/terra cotta garden pots from oxidizing.
>13) Removes tomato stains from clothing.
>14) Keeps glass shower doors free of water spots.
>15) Camouflages scratches in ceramic and marble floors.
>16) Keeps scissors working smoothly.
>17) Lubricates noisy door hinges on vehicles and doors in homes
>18) It removes black scuff marks from the kitchen floor! Use WD-40 for
>those nasty tar and scuff marks on flooring. It doesn't seem to harm the
>finish and you won't have to scrub nearly as hard to get them off. Just
>remember to open some windows if you have a lot of marks.
>19) Bug guts will eat away the finish on your car if not removed quickly!
>Use WD-40!
>20) Gives a children's play gym slide a shine for a super fast slide.
>21) Lubricates gear shift and mower deck lever for ease of handling on
>riding mowers.
>22) Rids kids rocking chairs and swings of squeaky noises.
>23) Lubricates tracks in sticking home windows and makes them easier to
>open.
>24) Spraying an umbrella stem makes it easier to open and close.
>25) Restores and cleans padded leather dashboards in vehicles, as well as
>vinyl bumpers.
>26) Restores and cleans roof racks on vehicles.
>27) Lubricates and stops squeaks in electric fans.
>28) Lubricates wheel sprockets on tricycles, wagons, and bicycles for easy
>handling.
>29) Lubricates fan belts on washers and dryers and keeps them running
>smoothly.
>30) Keeps rust from forming on saws and saw blades, and other tools.
>31) Removes splattered grease on stove.
>32) Keeps bathroom mirror from fogging.
>33) Lubricates prosthetic limbs.
>34) Keeps pigeons off the balcony (they hate the smell).
>35) Removes all traces of duct tape.
>36) Folks even spray it on their arms, hands, and knees to relieve
>arthritis pain.
>37) Florida's favorite use is: "cleans and removes love bugs from grills
>and bumpers."
>38) The favorite use in the state of New York WD-40 protects the Statue of
>Liberty from the elements.
>39) WD-40 attracts fish. Spray a LITTLE on live bait or lures and you will
>be catching the big one in no time. Also, it's a lot cheaper than the
>chemical attractants that are made for just that purpose. Keep in mind
>though, using some chemical laced baits or lures for fishing are not
>allowed in some states.
>40) Use it for fire ant bites. It takes the sting away immediately and
>stops the itch.
>41) WD-40 is great for removing crayon from walls. Spray on the mark and
>wipe with a clean rag.
>42) Also, if you've discovered that your teenage daughter has washed and
>dried a tube of lipstick with a load of laundry, saturate the lipstick
>spots with WD-40 and re-wash. Presto! Lipstick is gone!
>43) If you sprayed WD-40 on the distributor cap, it would displace the
>moisture and allow the car to start.
>P. S. The basic ingredient is FISH OIL.